\documentclass{amsart}
\usepackage{amsthm}
    \newtheorem{theorem}    {Theorem}       [section]
    \newtheorem{lemma}      [theorem]       {Lemma}
    \newtheorem{cor}        [theorem]       {Corollary}
    \newtheorem{prop}       [theorem]       {Proposition}
    \newtheorem{example}    [theorem]       {Example}
    \newtheorem{definition} [theorem]       {Definition}
\begin{document}
    \author{PUT AUTHOR(S) HERE}
    \title{PUT TITLE HERE}
    \address{University of Illinois at Urbana-Champaign}
    \email{PUT NETID HERE\char`\@uiuc.edu}
    \urladdr{http://www.uiuc.edu/\char`\~PUT NETID HERE/}
    \date{\today}
\maketitle
\section*{Introduction}

PUT INTRODUCTION HERE.

\section{PUT SECTION TITLE HERE}

PUT CONTENTS OF FIRST SECTION HERE.

\end{document}
