First of all, Is your modem Linux compatible or does it need windows drivers, a winmodem? If it is a winmodem, take it back to whoever you bought it from and get another one.
If it knows the "AT" commands, then go get the program minicom and make sure that you can setup the modem to connect to another telephone. Likewise, you have to be able to call the modem and get the "whistle".
Go look at the site "http://tldp.org/HOWTO/html_single/Modem-HOWTO/". It will show you how to connect your modem.
Until you can dial in and out using the modem, don't even worry about the FAX software.
The Fedora crew has mucked around /etc/inittab (which wasn't broken) so I don't know how you even setup a process that listens to a /dev/ttyS? port anymore.