It is always convenient and helpful to have a (clickable) TOC while we are preparing for our publications. It will give us a big picture of our work.
Put the piece of code I provided below immediately before your \section{Introduction} in your .tex file, you will have a clickable TOC in your tex created pdf! Happy Writing:)!
\newpage \thispagestyle{empty} \setcounter{tocdepth}{4} \normalsize \tableofcontents \normalsize \newpage %\pagestyle{fancy} \setcounter{page}{1} \setcounter{section}{0} %\cfoot{\small \sffamily \thepage} \pagenumbering{arabic}