So I just wandered over here by accident, since I spend my time in the Nortel PBX forum.
I have to say that you guys seem to be a little harsh. Last I checked this is a place where all users can share and ask questions. True, most answers can be found in the manuals, but everyone needs to start out somewhere.
I'm not telling you how to act, or what to think. If you feel the way you do, that's fine. Maybe another way of not helping is just to ignore posts from users like this. Some folks are here to offer help to anyone.
Just an opinion from someone willing to help anyone get on there way.
So now for another way of answering this question:
DID's are mapped to Target Line buttons on specific phones, this can be a little complicated at first, so after reading up on Target Lines, maybe you want to contact a vendor to do this for you this time around, but pay close attention to the process so in the future you can do this yourself.
Once you understand the simple process and logic behind it, this is something that is easily done. The BCM documentation is available on the Nortel website at
http://nortel.com/documentation. You'll need to register first, but will have access to all of the information you should need after you do.