\documentclass{report}
\usepackage[utf8]{inputenc}
\usepackage[backend=biber]{biblatex} % I try to use biber.
%this might not work in online TeX compilers
%\addbibresource{ref} % the ref.bib file
% and this should work
\bibliography{./ref} % the ref.bib file
\begin{document}
Hi there, Stackoverflowers\cite{lol}
\printbibliography
\end{document}
