How do I use the frontespizio package?

The frontespizio package typesets a frontispiece in a style suitable for a thesis at an Italian university. It produces the frontispiece as a separate PDF, which is then included back into the main project. This means that a special compile step is required, in order to build the frontispiece. To achieve this on Overleaf, you can use \write18 to start the compile, like this:

\begin{frontespizio} 
\Istituzione{Politecnico di Torino}
% ... your other information here
\end{frontespizio}
\IfFileExists{\jobname-frn.pdf}{}{%
\immediate\write18{pdflatex \jobname-frn}}

If the compile of the frontispiece fails, you can use the listings package and then put

\lstinputlisting{output-frn.log}

after the code above to get the log file into your main project, where you can read it and find the issue.

Note that if you're using the LuaLaTeX compiler, you will need to add

\usepackage{shellesc}

to your preamble for this to work, to make the \write18 or \ShellEsc commands available to LuaLaTeX.