\documentclass{beamer}

\author{Joel}
\title{Title}

\begin{document}

\begin{frame}
  \maketitle
\end{frame}

\begin{frame}{contents}
  \tableofcontents
\end{frame}

\section{section1}
\subsection{subsection1a}

\begin{frame}{frame}
  \begin{itemize}
    \item One
    \item<2-> Two
    \item<3-> Three
  \end{itemize}
\end{frame}

\end{document}
