Establish or verify an INTERNET connection (preferably broadband), launch G3, select ->.Multiplayer->Host. Give your session a name, pick max number of users and click OK. It is that simple really, unless you have a firewall or port blocking issues. even in this case, let us or KnifeEgde know what you have going on and we can sort it out. No need to change port address or anything else on the Host screen.

Have you 'Joined' any multi-player sessions? If you want, PM me some time and I will set up a session to test connectivity with you. We can then also verify your ability to host also. You don't list a geographic region, but I am on the east coast and normally available after 1800hrs. (6:00pm) EST/EDT.