Here's part of it (exluding ISDN stuff, since we don't offer it)
Typical PPP account:
someusername<tab>Password = "thepassword", Expiration = "May 14 1997"
<tab>Ascend-Idle-Limit = 1200
<tab>Framed-Protocol = 1
<tab>User-Service = 2
Of course, replace the "<tab>" with an actual keyboard tab.
The 1200 is 1200 seconds (20 minutes).
Make sure that there is a blank line after the last entry and DON'T use the
command-line based EDIT to edit the file.