I am assuming you just bought this rig used. Do you also have a receiver? This is a box that looks a lot like a cable box that is connected to your TV. If you have a receiver, you need to have an account with DISH or DirectTV and pay a monthly fee. You also should have some sort of little square box that contains a controller for the motor that turns your satellite around so it can find a signal.
And, I suppose the last question is, are you sure you have a satellite under the satellite dome on top of your rig? It is possible, I suppose, that the seller removed it and left the dome. You might have to go up on the roof and check.
When all of this is working, you should hear the motor turning the satellite around searching for a channel. Do you hear anything when you are plugged into electric service and the receiver and satellite controller are plugged in?
If you are missing components, you still ought to be able to get air TV with the regular antenna you have on top of your rig, assuming you have an antenna on top of your rig. Have you checked? There should be a handle inside that you use to crank it up and turn it around like the old rabbit ears to find an air channel.
