You have a 120V AC television, correct?
Is there an AC outlet near the TV?
Even if there isn’t, wire the inverter directly to the battery (fused) or nearby off the 12V fuse panel/distribution block. If direct from the battery doesn’t matter which battery if they’re 12v batteries in parallel. If 6V series wires batteries then you need to hook to the +/- posts going to the load, not the series jumper wire posts.
Wire the inverter into the AC electrical system in the camper then you can use the inverter off of any plug in the camper.
Then plug in TV direct or ext cord from a 120v outlet somewhere.