\documentclass{article}
\usepackage{graphicx}
\usepackage{hyperref}

\begin{document}

\title{My Great Theory}
\author{John Doe}
\date{May 1, 2020}

\maketitle

\begin{abstract}
A simple paper with manual bibliography management.
\end{abstract}

\section{Introduction}
Here is the text of your introduction of the background ~\cite{lamport}.
\section{Problem and Solution}

\subsection{Problem}
Describe the problem.  

\subsection{Solution}
Write your solution here ~\cite{website}.

\section{Conclusion}
Write your conclusion here.

\begin{thebibliography}{9} % We usually have less than 10 items
\bibitem{lamport} Leslie Lamport, \emph{LaTeX: A Document Preparation System}.
\bibitem{website} \url{https://texwriter.net}.
\end{thebibliography}

\end{document}