from what i recall you need to run a cable from the switch +ive to a 12v supply. you also need an acc switch running cable to the boot and connect this upto the bulb thats closest to the tailgate (make sure you connect it to the 21w system and not the 5w, easiest way is to snip the wires and when you connect them, see which one is brighter).
if you have an aftermarket switch then you need to connect an earth to it and for the acc switch you need to have it go from the switch to the dipped beam circuit, and then onto the rear lights
if you want to have 2 fog lights like me then all you do is wire up the other side in exactly the same way, taking a spur from the o/s.
i will double check this for you as ive got to wire my fogs from an aftermarket switch into the factory switch at some point!