Getting a Program to work with a firewall

[wonderworm2000]

I have installed phone software that I would like to try and I have a compaq wireless router. The software says my router isn't configured properly for it to work. It works when you bypass the router. It also works with the router on net2phone, but I would like to try some different software with better sound processing. The one I'm trying to get to work is Internet Switchboard software from QuickNet. It appears I need to open specific ports in the router for it and the software has a place to make changes. I've done quite a bit of working around in my router before on other things, but I don't know much about ports. Can anyone explain to me how they work and where I need to make the needed changes to get my program to work through the router?
Thanks for the help