You don't state your version that would allow me to give step by step
details, so here's the basics.

You upload the file to the server.
You have to know where you put it so you know it's address (url).
For example you put it in the web root -
the url is www.mysite.com/myfile.pdf
or you put it in a directory -
www.mysite.com/myfolderhere/myfile.pdf

You then use that url for the link.
Right click the text or image being hyperlink, select hyperlink,
and in the hyperlink dialog (differs by version) you use the URL.