how to cite in latex overleaf code example

Example 1: overleaf bibtex file

\usepackage[style=ieee, citestyle=numeric-comp, backend=biber]{biblatex}

\addbibresource{reference.bib}

\begin{document}



\printbibliography

\end{document}

Example 2: cite bibliography latex

//Build a bibliography
\begin{thebibliography}{99}

\markboth{ }{\textsl{Bibliography}}

\addcontentsline{toc}{chapter}{Bibliography}
\bibitem{A} Author, \emph{Title}.
\end{thebibliography}

//Cite somewhere in the text
...as cited in the book \cite{A}