how to add colspan in overleaf

Question

I have this code but I want to add 1 more subcolumn for (2nd and 3rd column) in my table like this figure in screenshot

  \documentclass[conference]{IEEEtran}
    \IEEEoverridecommandlockouts
    %\usepackage{cite}
    \usepackage{amsmath,amssymb}
    \usepackage{algorithmic}
    \usepackage{graphicx}
    \usepackage{textcomp}
    \usepackage{xcolor}
    %\usepackage{subfig}
    \usepackage[english]{babel}
    \usepackage{makecell}%
    %table
    \usepackage[margin=1in]{geometry}
    \usepackage{tabularx, booktabs}
    \newcolumntype{Y}{>{\centering\arraybackslash}X}
    
    \usepackage{times}
    
    \makeatletter
    \newcommand{\removelatexerror}{\let\@latex@error\@gobble}
    \makeatother
    
    %\documentclass{IEEEtran}
    
    \usepackage[english]{babel}
    \usepackage[utf8]{inputenc}
    
    \def\BibTeX{{\rm B\kern-.05em{\sc i\kern-.025em b}\kern-.08em
        T\kern-.1667em\lower.7ex\hbox{E}\kern-.125emX}}
    \usepackage{subcaption, floatrow}
    
    \begin{document}
    
    \begin{table*}
    \begin{subfloatrow}[2]
    \CenterFloatBoxes
    \ttabbox{\caption{aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa}\label{tbl}}
    {\tiny \setlength\tabcolsep{3pt}\centering
    \begin{tabular}{@{} ll *{4}{c} @{}}
    \toprule
    ooooooooo& bbbbbb
      &\multicolumn{2}{c}{ccccvvvvvv}
      &\multicolumn{2}{c}{ccccccccc}\\
    \cmidrule(lr){3-4} \cmidrule(l){5-6}
     & & \makecell{vvvvvvvvv\\ (cccc)} &\makecell{vvvvvvvvv\\ (vvvvvvv)} &\makecell {vvvvvvvvv\\ (cccc)} &\makecell {vvvvvvvvv \\ (vvvvvvvv)} \\
    \midrule
    vvvvvvvvvvvvvvvvv & bbbbbbbbb &fff &fffffffff &fffffffffffffff& ff \\
    \addlinespace %\midrule
    ffffffffffff & fffffff8 &fff &fffffffffffff & ff &fffffffffff\\
    \addlinespace %\midrule
    fffffffffff & ffffffffff &fff &ffffffffff & ffff &ffffffffff\\
    \addlinespace %\midrule
    fffffffff & fffff &fff &fffffffffffff &fff &fffffffffffff\\
    \addlinespace %\midrule
    ffffffffffffffff & ffffffff &fff &ffffffffffff4 &ffffffffff& ff \\
    \addlinespace %\midrule
    fffffffff & fffffff &fffffff &fffffffff &ffffffffffffff& ff \\
    \addlinespace %\midrule
    fffffffff & ffffffff &fff &ffff &fffffffffffff& ff\\
    \addlinespace %\midrule
    ffffffffffffffff & ffffffffff &8fffff &ffffffffffff &ffff& fffffffffffff\\
    \bottomrule
    \end{tabular}}
    \killfloatstyle
    \hskip 6em
    \ffigbox [\FBwidth]{\raggedleft\includegraphics[scale=0.7]{Nightmare_Fussli}}
     { \caption{Johann-Heinrich Füssli: Nightmare}\label{fig}}
    \end{subfloatrow}
    \end{table*}
    
    \end{document} 

Answer 1

I guess that you looking for something like this:

Above table is produced by the following MWE:

\documentclass[conference]{IEEEtran}
\IEEEoverridecommandlockouts

\usepackage[margin=1in]{geometry}

\usepackage{textcomp}
%\usepackage{times}
\usepackage{booktabs, makecell, tabularx}
\newcolumntype{Y}{>{\centering\arraybackslash}X}
\usepackage{capt-of}
\usepackage[export]{adjustbox}  % for "valign", it also load graphicx

\begin{document}
    \begin{table*}[ht]
    \begin{tabularx}{\linewidth}{>{\hsize=1.2\hsize}Y
                                 >{\hsize=0.8\hsize}Y}
\caption{aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa}
\label{tbl}
    \setlength\tabcolsep{0pt}
    \small
\begin{tabular}{@{\extracolsep{\fill}} ll *{6}{c} @{}}
    \toprule
ooooooo 
    & bbbbbb 
        &\multicolumn{3}{c}{ccccvvvvvv} 
            &\multicolumn{3}{c}{ccccccccc}  \\
    \cmidrule(lr){3-5} \cmidrule(l){6-8}
    &   &   \makecell{vvvv\\ (aaaa)} 
            &   \makecell{vvvv\\ (bbbb)} 
                &   \makecell{vvvv\\ (cccc)}
                    &   \makecell{vvvv\\ (aaaa)}
                        &   \makecell{vvvv\\ (bbbb)}
                            &   \makecell{vvvv\\ (cccc)}   \\
    \midrule
vvvvv
    &   bbbbbbb
        &   fff 
            &   ffff
                &   fffff
                    &   fff
                        &   ffff
                            &   fffff                            \\
    \addlinespace
fffff
    &   fffffff8 
        &   fff 
            &   fffffffffffff 
                &   ff 
                    &   fff
                        &   fffffffffffff
                            &   ff                              \\
    \addlinespace
vvvvv
    &   bbbbbbb
        &   fff
            &   ffff
                &   fffff
                    &   fff
                        &   ffff
                            &   fffff                            \\
    \addlinespace
fffff
    &   fffffff8
        &   fff
            &   fffffffffffff
                &   ff
                    &   fff
                        &   fffffffffffff
                            &   ff                              \\
    \bottomrule
\end{tabular}
    &   \includegraphics[width=\linewidth,valign=t]{example-image-duck}%{Nightmare_Fussli}
        \captionof{figure}{Johann-Heinrich Füssli: Nightmare}
        \label{fig}
\end{tabularx}
    \end{table*}
\end{document}

Addendum: For exercise (and advertising a new LaTeX-3 package) :-)

If you allowed to use tabularray package, than design of placement of the your table and image can be even better:

\documentclass[conference]{IEEEtran}
\IEEEoverridecommandlockouts

\usepackage[margin=1in]{geometry}

\usepackage{newtxtext, newtxmath}  % instead of textcomp or times fonts
\usepackage{tabularray}
\UseTblrLibrary{booktabs, counter, varwidth}

\usepackage{capt-of}
\usepackage[export]{adjustbox}  % for "valign", it also load graphicx

\begin{document}
    \begin{table*}[ht]
     \small
     \setlength\tabcolsep{3pt}
    \begin{tblr}{colspec={@{} X[1.3,c] X[0.7,c] @{}},
                      measure = vbox}
%
\begin{talltblr}[
\caption={aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa}
\label{tbl}         ]{colspec={@{} ll *{6}{c} @{}},
             colsep={3pt},
             }
    \toprule
ooooooo 
    & bbbbbb 
        &   \SetCell[c=3]{c}    ccccvvvvvv  &   & 
            &   \SetCell[c=3]{c}    ccccccccc   &   &   \\
    \cmidrule[lr]{3-5} \cmidrule[l]{6-8}
    &   &   {vvvv\\ (aaaa)}
            &   {vvvv\\ (bbbb)}
                &   {vvvv\\ (cccc)}
                    &   {vvvv\\ (aaaa)}
                        &   {vvvv\\ (bbbb)}
                            &   {vvvv\\ (cccc)}   \\
    \midrule
vvvvv
    &   bbbbbbb
        &   fff
            &   ffff
                &   fffff
                    &   fff
                        &   ffff
                            &   fffff                            \\
vvvvv
    &   bbbbbbb
        &   fff
            &   ffff
                &   fffff
                    &   fff
                        &   ffff
                            &   fffff                            \\
vvvvv
    &   bbbbbbb
        &   fff
            &   ffff
                &   fffff
                    &   fff
                        &   ffff
                            &   fffff                            \\
fffff
    &   fffffff8 
        &   fff 
            &   fffffffffffff 
                &   ff 
                    &   fff
                        &   fffffffffffff
                            &   ff                              \\
vvvvv
    &   bbbbbbb
        &   fff
            &   ffff
                &   fffff
                    &   fff
                        &   ffff
                            &   fffff                            \\
fffff
    &   fffffff8
        &   fff
            &   fffffffffffff
                &   ff
                    &   fff
                        &   fffffffffffff
                            &   ff                              \\
vvvvv
    &   bbbbbbb
        &   fff
            &   ffff
                &   fffff
                    &   fff
                        &   ffff
                            &   fffff                            \\
fffff
    &   fffffff8
        &   fff
            &   fffffffffffff
                &   ff
                    &   fff
                        &   fffffffffffff
                            &   ff                              \\
    \bottomrule
\end{talltblr}
    &   \includegraphics[width=\linewidth, valign=m]{example-image-duck}%{Nightmare_Fussli}
        \captionof{figure}{Johann-Heinrich Füssli: Nightmare}
        \label{fig}
\end{tblr}
    \end{table*}
\end{document}