If you need an overall twocolumn layout, you could use the twocolumn
option.
If you want to have a figure with a caption inside the multicol
environment, you could use the caption package. The separation between the columns can be adjusted by the length columnsep
. The width of the columns depends on the available text width, of course. See the following example:
\documentclass{report}
\usepackage[T1]{fontenc}
\usepackage[latin1]{inputenc}
\usepackage{multicol}
\usepackage{lipsum}
\usepackage{caption}
\setlength{\columnsep}{3cm}
\begin{document}
\chapter{A chapter}
\begin{multicols}{2}
\lipsum[1-2]
\bigskip
\rule{0.8\columnwidth}{1cm}
\captionof{figure}{A figure}\label{figure1}
\bigskip
\lipsum[3]
\end{multicols}
\chapter{Another chapter}
See figure~\ref{figure1}.
\begin{figure}%
\rule{0.8\columnwidth}{1cm}
\caption{Another figure}
\label{figure2}
\end{figure}
\chapter{A third chapter}
See figure~\ref{figure2}.
\end{document}
(The lipsum
package is only for producing the sample text, it is not part of the solution.)