Extend ethernet network via moca on xfinity

So in my setup at my house all my laptop wireless adapters are pretty bad, and I lack a usb wireless adapter so I have to tether my phone. Large ethernet runs that are flush with the wall aren’t an option and I don’t want to deal with powerline, but I do have a coax output in my room, so how would I go about setting up moca to get ethernet to my room easier, do I need a box which converts the ethernet, or can I use the included modem and just buy a single converter? Other means have not given me a straight answer, and I hope that your experinces with large home networks can help.

This picture pretty much spells it out for you.

https://images-na.ssl-images-amazon.com/images/G/01/electronics/detail-page/sc_b008c1jc4o-02connectmaplg.jpg