PPP accounts are for users who dial in to your system via a modem.
Most of the parameters for a PPP account should be filled in the same as a regular login account, so see login if you need more information on login name, full name, home directory, user ID, and the mail settings.
You can't set the group for a PPP user; all PPP accounts are in the
pppusers group.
The default command interpreter or login shell for a PPP user is
/usr/lib/linuxconf/lib/ppplogin, which is a script for handling PPP
logins. If you have another command interpreter script for handling PPP logins,
you'll need to add it to linuxconf's choices using Config--Networking--Users
Accounts--Available PPP Shells.