How do you hook up wireless head phones to car tv?

You can try getting an FM transmitter. You can find them cheap on EBay (you get the quality you pay for. Cheaper transmitters have smaller broadcast range.)
With an FM transmitter plugged into your headphone jack on your car tv (I'm assuming it has one) you can tune your headphone radio into your transmitters broadcasting frequency, and there ya go. You could then connect many at once.
If you're asking about bluetooth headphones or something else, I can't help there.