Need Help With Server Development

Ok, I posted this on Moparscape but haven't gotten any help, so I'm posting here now. My friend and I are making a server. We were using the guide on Moparscape, http://www.moparscape.org/smf/index.php/topic,200036.0.html, and were going through it relatively quickly. We then got to Chapter 5, "Port Forwarding". We used the Command Prompt to find out his IP Address, found it, entered it into the address bar, and it said the page you entered doesn't exist. Ok. Then, we found out he doesn't have Linksys, he has Arris TM502G. On the aforementioned Moparscape page, there is a link to portforward.com, which we went to. There is a list of all other routers, except for his. My question: What are we supossed to do? Why is his IP Address not coming up? And what about the router? Thanks for reading and please help.