First off, are you talking about hooking up Cable TV - i.e. running the cable TV coax to a connector in the Universal Docking Center (UDC)? If so, you probably have 5 coax connectors there. 4 of them are in a row and are for satellite. The 5th is by itself, and may be located on one side of the UDC.
For Cable, the signal booster inside the coach (at one of the TV locations) must be OFF. The TV menu setting must be on Cable (some TVs now automatically select between AIR and Cable).
After all that is right, then run a channel scan.
If you're talking about over the air reception, the rooftop antenna is connected at the factory and the signal booster must be ON. TV menu set to AIR. Then run the channel scan. Depending on the type of rooftop antenna, you may have to adjust the direction of the antenna to get good reception.