I need assistance on conneting my HP OfficeJet 6978 printer to the network
Do you have a router with an open ethernet port to directly connect your printer? If not, if your printer has WiFi capability, you might be able to connect it to your home network using WiFi.
I have that exact printer. It is connected via Ethernet to my router. It also has WiFi capability if you want to use that. You then run the HP software so it can find the printer and set up the printer port and drivers.
Basically, there is nothing special about being on Comcast. Just follow HP's instructions. There are some videos on installing on the bottom of this page with driver and other downloads: