Here is one way to do the exercises. For this example, you’ll need an image file and a .bib file in your project, so the exact code will depend on your file names.
\documentclass{article}
\usepackage{graphicx,fancyhdr,amsmath,amssymb,amsthm,subfig,url,hyperref,booktabs, multicol, multirow}
\usepackage[margin=1in]{geometry}
%----------------------- Macros and Definitions --------------------------
%%% FILL THIS OUT
\newcommand{\studentname}{First Last}
\newcommand{\suid}{first.last}
\newcommand{\exerciseset}{Homework N}
%%% END
\renewcommand{\theenumi}{\bf \Alph{enumi}}
%\theoremstyle{plain}
%\newtheorem{theorem}{Theorem}
%\newtheorem{lemma}[theorem]{Lemma}
\fancypagestyle{plain}{}
\pagestyle{fancy}
\fancyhf{}
\fancyhead[RO,LE]{\sffamily\bfseries\large School}
\fancyhead[LO,RE]{\sffamily\bfseries\large OPER ???}
\fancyfoot[LO,RE]{\sffamily\bfseries\large \studentname: \suid @school.edu}
\fancyfoot[RO,LE]{\sffamily\bfseries\thepage}
\renewcommand{\headrulewidth}{1pt}
\renewcommand{\footrulewidth}{1pt}
\graphicspath{{figures/}}
%-------------------------------- Title ----------------------------------
\title{OPER ???: Course \exerciseset}
\author{\studentname}
%--------------------------------- Text ----------------------------------
\begin{document}
\maketitle
\section*{Problem 3: Images}
Include any.png image:
\begin{figure}[h]
\centering
\includegraphics[width = 0.5\linewidth]{myimage1.png}
\caption{My Image}
\end{figure}
\section*{Problem 4: References}
\begin{enumerate}
\item %A
An in-line citation: \cite{Krishnamurthy2007}
\item %B
Bibliography:
\bibliographystyle{plainnat}
\bibliography{Mendeley.bib}
\end{enumerate}
\end{document}