D-Link VoiceCenter DVG-3104MS Quick Install Manual page 7

Select the D-Link DVG-3104MS Gateway you just connected and
click Next to continue.
Select the This Port Is Active check box. Enter in a phone number
or name associated with this line in the Description box. Click Next
to continue.
Enter a name for the phone line adapter and click Finish to complete
the configuration.
 D-Link DVG-3104MS Quick Install Guide