How do I open up ports for games on my netgear router?

If you're only trying to play a LAN game, then you don't need to open any ports on your router. Opening ports on the router is needed when you wish to have someone from the internet, not on your LAN, try to connect to you. However, if you do have firewalls on each of the computers, you will need to open these ports in the firewall (or completely disable it while playing, either way).