If you don’t see a “Documents” link in the main menu (across the top of the site), then you are most likely not logged in. Click “Login” in the main menu, type your credentials, and hit “Submit”.
If for some reason, you just logged in and can’t see the “Documents” link, that is most likely a cookie issue. Just refresh the page (or hit F5) and the “Documents” link should appear. If not, contact the webmaster.