Second IP address for SB 8200

Hi - I recently upgraded my modem to an SB 8200 which contains two Ethernet ports that can run to two different devices. I learned from the manufacturer and this thread that in order to get a second IP address I need Comcast's help.

https://forums.xfinity.com/t5/Your-Home-Network/Second-IP-Address-needed-for-SB8200/td-p/3311835

Can anyone help or point me in the right direction?