I just set up one yesterday that when you set it up, it adds TWO printers. One is a printer printer, and the other prints to the fax. When you go into the print dialog after selecting the fax print, change the view from pages/copies to fax settings. set the number and hit print.
I've set up a dozen of these in the last few years and that's how they all work. You don't set up a fax, it works as a printer. This particular one was integrated into Addressbook even.
