how to add a jpg image in Latex

You need to use a graphics library. Put this in your preamble:

\usepackage{graphicx}

You can then add images like this:

\begin{figure}[ht!]
\centering
\includegraphics[width=90mm]{fixed_dome1.jpg}
\caption{A simple caption \label{overflow}}
\end{figure}

This is the basic template I use in my documents. The position and size should be tweaked for your needs. Refer to the guide below for more information on what parameters to use in \figure and \includegraphics. You can then refer to the image in your text using the label you gave in the figure:

And here we see figure \ref{overflow}.

Read this guide here for a more detailed instruction: http://en.wikibooks.org/wiki/LaTeX/Floats,_Figures_and_Captions

if you add a jpg,png,pdf picture, you should use pdflatex to compile it.