\document[12pt]{article}
 % orizw tin kodikopoiish tou koimenou 
\usepackage[utf8]{inputenc}
 % orizw thn kvdikopoihsh ths grammatoseiras 
\usepackage[T1]{fontenc}
 \usepackage[english]{babel}
 \author{Nopi Tsartsari}
 \title{My title} 
 \date{2/3/2023}
 \begin{document} 
 \maketitle
 \section{My first section}
  This is my first section
 \subsection{This is my subsection}
  This is my first subsection
 \end{document}
