A 'How-to' question... Son's XBox to my CGM4141 Panoramic router/modem/phone controller

In August of 2019 we upgraded to the new 3.1 DOCSIS standard by getting the 'CGM4141' Panoramic Gigablast router/modem/phone controller. It has been great along with the highest tier for upload/download web speed.

Now, I want to set up on my computer desk, in addition to my current desktop computer which is already there, my son's Xbox. The Xbox needs an internet connection and an ethernet connection, correct? Now, the CGM4141 is connected to my computer and it's 2 ethernet ports are both being used.( One to my computer, the other to my wife's computer in the room also).  So, I have no ethernet port for the Xbox...... Help.... 

Brian in Johnston, RI