How to make my IP address public?

So I had a 7yr old modem and 5yr old router that died a couple weeks ago.AT&T sent me a brand new Netgear 7550 modem/router combo. Since setting it up, all my wireless devices (Laptop, Xbox, iPhone) have been performing terribly when I try to play Xbox Live or stream music, and after investigating on different forums, I have learned that if I set my IP address to be public, then it should work fine. None of said forums have given me any info on how to do so. If anyone could give me a step-by-step walk-through on this, it would be greatly appreciated.

It not to set your ip address to be public. Just set the networking to be DHCP. You can look at manual of the modem how to do this.

Yeah, like the other guy said, you want to enable NAT/DHCP. If that doesn't work, read about port forwarding, but you shouldn't have to do that. (Side note, your IP already is accessible to the public, its just that your router doesn't allow connections through most ports for safety.)