Home Wireless In Setting Up A Home Wireless Network Can I Leave The Main Computer Connected To The Cable?

In setting up a home wireless network can I leave the main computer connected to the cable? - home wireless

I have a desktop computer with Comcast Cable Internet. I want to go to a home wireless network for family members or laptops in other rooms to create work, but I want my office to leave cable. How can I connect them? It seems that the cable-modem cable or my office or a router is connected, but not both. Is there another way?