Fitted a set of these the weekend and even for a complete DIY idiot like myself, it was pretty straight forward.
Just for reference if you pull off the cover for where the jack is kept, just above it is the main wiring loom for the rear of the car. Unwrap the black tape or protective cover and you will have lots of different coloured wires. The reverse light one is Orange. I tested by turning on ignition (not engine) putting car in reverse and then stab the wires with my mutimeter till I got a 12v reading (managed to stab my hands quite a bit).
There is also a earthing point about 12 inches down from the Brake lights on the inside passenger of the vehicle (Just remove the door strip and pull at the plastic surround and you will see them). The version of Parking Sensors I had didnt need a wire to be ran from the back to the front of the car as it was wireless signal. For the display thingy at the front of the car I wired into the cigerette lighter as it works off a 12v ignition live and has an earth wired there also.
Only other things I did is turn the 2 outside sensors upside down, this is because they are all disigned with the top of the sensor slighty thicker than the bottom, so to get the so the point a tad down I turned them around.
Tested that they were all working by walking past each one.