I have the same setup at home.

Let me see if I can walk you through it.

So you'll need 3 separate lines of coax cable. If you have that, and a spliter that has one port on one side, and two or three on the other side, you should have enough to do it.

One cable screws on to the wall. At the end of that cable, the splitter screws on. Then the second cable screws onto the splitter, then to the tv. Then the third cable screws on to the splitter and then to the cable modem.

Did that help at all???