I have only ever done this on the NM-16DM with PRI on a 3600 router, but I imagine the modules you have will configure in much the same way.
The key command is on the PRI control channel interface, and is the line
isdn incoming-voice modem
which makes sure the incomming isdn call from the remote user goes to the digital modem card, and the router can then handle it ok. If the PRI config and that command are there, dial the ISDN number from a normal phone and you should hear the modem answer.
Have a look at http://www.cisco.com/en/US/tech/tk801/tk36/technologies_configuration_example09186a0080094898.shtml
which should get you going. If you are in Europe, the control channel number is 0:15 and the switrch type is Primary-net5 from memory (please check as the old memory aint what it used to be !!).
Hope this helps.