How do I change my NAT settings on my router for my Xbox 360?

I think I need to change the settings to open. I’ve never been on xbox live nor can I hook into it (we have satellite internet) so I don’t know if I even have an IP address I can use. I need to change it because Saints Row 2 is constantly freezing up when my friend and I play. I’m not too much of a techie, so Laymans terms as best as possible please. Thank you!