first depends on your radio, second, you need to have the dealer "flash" the radio to accept a camera.
Just went thru that with my 2011 ram. I'm using the stock radio (430 RBZ) and put a license plate camera on for my trailer hook up. You have to run the wires first and get the camera all hooked up so the dealer can see if the flash worked or not. I ran my RCA cable thru the inside of the frame to the front of the truck and into the dash via the fire wall.
I should also tell you you have to get a harness adapter for the back of the radio. I forgot the part number, but it was only like 20 bucks or so. Some cameras you can buy have active parking lines (means they move with the steering wheel) My BOYO camera did that but it burned out for some reason (maybe not as waterproof as they claimed) so i bought a cheap camera for 24 bucks and it's great.