Handbook:Basic Server Configuration:Faxaddmodem
Modems are configured for use with the faxaddmodem script. This is an interactive script that walks you through the configuration and installation of a new or existing modem. Even if you have a previous version of HylaFAX or FlexFAX installed it is a good idea to run faxaddmodem to update the configuration information for your modems after installing a new distribution.
faxaddmodem may be run directly from the command line or via the faxsetup script that is used to prepare a server machine for use with HylaFAX.
It would be nice to have a properly formatted walk-through with examples and explanation of each question here - DPN.