rf modulator means it connects to your car arial socket and you 'tune' your stereo to the dvd players channel.means you dont have to hook up any wires to the speakers. problem is if you have a good set up it will only sound as good as a radio station and not dvd/cd quality.
all you would need to do then is hook up the video connections to the screen/s and then hook up the rf modulator to the dvd player. obviously you need to sort out power etc fro both