Once you know the IP of your computer on your LAN, ipconfig /all. You can set your port forwarding to that address. You need to forward two sets of ports 47624 and 2300-2400. I will warn you to check your DSL/Cable Modem. If you are conecting through a router, you need to set your modem on bridge mode.
You can also set your computer in a DMZ while you play, but this results in reduced security to your computer from outside intrusion.
Tuscarora
Use portforward.com for reference if you need any.