\documentclass{article}
\title{Exercise on Lists in LATEX }
\author{}
\date{}
\begin{document}
\maketitle
Summer:
\begin{itemize}
\item June
\item July
\item August
\end{itemize}
Prepare for summer:
\begin{enumerate}
\item Get fit
\begin{enumerate}
\item Jogging
\item Press-ups
\item Learn to swim
\end{enumerate}
\item Buy summer clothes
\item Buy tickets
\end{enumerate}
\end{document}