Configure another dial-out machine 

"How to Configure the Modem and Serial Port (Dial-out Machine)".

Test modem connectivity by dialing out to a another computer 

cu(1C) and tip(1) man pages. These utilities can help you test if your modem is properly configured and can establish a connection with another machine.

Get detailed information about the PPP configuration files 

"Using PPP Options in Files and on the Command Line".

Begin configuring the dial-in server 

"Configuring Devices on the Dial-in Server".