The "site" was your router. The router lives at 192.168.1.1. Go there and, on the main page, disable the DHCP server.
Then you have to go into your computer and set it to "Use the folllowing IP address" and pick one - say 192.168.1.50. Also put in 2 of the DNS addresses from the main page of the router (Static DNS1 and Static DNS2).
Now forward your ports (whatever range you're using for DCC and 113 for IdentD) to 192.168.1.50.
If you have any other computers connected to that router you're going to have to use a static address on them too - anything from 192.168.1.2 to 192.168.1.254 that's not being used by another computer. (192.168.1.1 is being used by the router and 192.168.1.50 is being used by the computer you just set up.)
Notice that none of this has anything to do with Comcast, just your computer and your router.
These are the very basic steps, like boiling water to make a soufle. If you can't learn to boil water, being a chef isn't a good choice for you.
