\documentclass{article}
\usepackage{graphicx}
\title{Pictures in \LaTeX}
\author{}
\date{}
\begin{document}
\maketitle
Medieval artists sometimes tried to incorporate pentagons in their ornaments; see Fig. \ref{fig:esf}. However, this is impossible for a regular ornament, by a theorem in Group Theory. One can see irregularities in Fig. \ref{fig:esf}.
\begin{figure}[h]
\centering
\includegraphics[width=\textwidth]{esf}
\caption{Ornament with pentagons in Esfahan}
\label{fig:esf}
\end{figure}
\end{document}