After talking with support techs for two hours who couldn't help and with one tech so frustrated he said I should just buy my own equipment because COX will eventually change it again, I poked around and found it myself. Hopefully it's there for you as it is for me. Login to your Gateway as normal, click on the ADVANCED tab then WIFI.COX.COM, click on the NETWORK tab, Under NETWORK DEVICES click on the GATEWAY box, Scroll to the bottom and under MORE, click ADVANCED SETTINGS, then PORT FORWARDING.
This was supposed to make it easier for the novice to set up ports, totally ignoring the people like me who can set up their own ports. They failed.