If you can't see it via "Find Local Game," that may have to do with your firewall, but it's not a big deal. You can directly enter "127.0.0.1" in Connect to IP address to get into the game. If you were entering your public IP address, that would try to go out through your router, to your ISP, and back to your machine, which would get blocked by your router.
If 127.0.0.1 doesn't work for some reason, then the things to check are 1) is your actual game client set to the same port as the server if you changed the port on the server? 2) is your local software firewall somehow blocking you? The latter seems unlikely given your friends are in.
Most likely it's just that you need to use 127.0.0.1. Hope that helps!