Its easy to wire.
You need a relay, a switch (if you want to switch them on and off with low beams), wire, female spade terminals (x4), waterproof connectors to your foglight wires, and a fuse. (And probably some other terminals, whatever you decide to use for connections).
Run a trigger wire off the positive wire into one of your low beams. (Check for + voltage with a DVOM). One is +, one is -. You need to tap into the + wire. Run that to the switch (if you want to switch them, then from the switch to the coil), or to the coil side of the relay. Run a ground off the other end of the coil. This will be the trigger to turn them on and off. Then you find a constant 12V source, and run a fused wire to your relay. Then the other side goes out to your fog lights as their +12V input. Run your grounds off the lights to a piece of metal behind the bumper. Use waterproof connections to your lights, as they will be out in the elements (at least mine are, since the leads are very short).
Now you should be able to turn on your low beams, and fogs should come on (or flip the switch if you wired it in). Now turn on your high beams. The fogs should go out on their own. Without a +12V reference from the low beams, the relay opens and shuts them off.
Not that difficult.