You can use a one-column tabular environment to wrap the figure (in the first row) and the note (in the second row). A little example:
\documentclass{article}
\usepackage[demo]{graphicx}
\usepackage{hvfloat}
\usepackage{lipsum}% just to generate some text
\begin{document}
\hvFloat[%
floatPos=p,%
capWidth=1.3,%
capPos=t,%
rotAngle=90,%
objectPos=l]
{figure}
{
\begin{tabular}{c}
\includegraphics[width=0.9\textheight, height=0.7\textwidth]{cat}\\
\multicolumn{1}{c}{\parbox{0.7\textheight}{\fontsize{8}{8}\selectfont\lipsum[1]}}\end{tabular}
}
[Caption in ToC]{Figure caption}{fig:resqrbd}
\end{document}
The demo option for graphicx was only used to make my example compilable for everyone; do not use this option in your actual code.
