Just copy the link of the file and paste it in the [ url][/url]  thing. It should look like this:

http://google.com/

And if you want to give a name to that hyperlink do the following:
1-in the first bracket e.g. [ url][/url] put a = so it looks like this - [ url=][/url]
2-put the link after the = sign -> [ url=http://google.com/][/url]
3-give that hyperlink a name as you type it between the two brackets -> [ url=http://google.com/]<name>[/url] and it should look like THIS

I knew that... anyway thanks