The next commands are the ones that set the bibliography style and import the bibliography file. See Bibliography management with biblatex for more information.

%in the preamble
%--------------------------------
\usepackage[
backend=biber,
style=stylename,
]{biblatex}

%--------------------------------

%Where the bibliography will be printed
\printbibliography

where bibfile is the name of the bibliography .bib file and stylename is one of the following:

stylename output
numeric
alphabetic
authoryear
authortitle
verbose
draft

The draft style is intended for editing your document before the final version, since it makes easier to keep track of the cited sources.

There are some additional bibliography styles you can use in Overleaf

stylename output
authoryear-icomp
apa
bwl-FU
chem-acs
chem-angew
chem-biochem
chem-rsc
ieee
mla
musuos
nature
nejm
phys
science
geschichtsfrkl
oscola

More styles can be found in the CTAN biblatex site