You use a philips head screw driver, just insert it where it through the little plastic slots, make sure it's a large philips, otherwise you'll just succeed in striping it out. I don't exactly remember which direction to turn it or which one it is, but just do it at night against a flat wall, and you'll be able to see it move ever so slightly. Either way, just remember that your left side is supposed to be a tad bit lower than the right light...on a wall from about 6 feet, it should be about an inch lower give or take some. Either way, don't make your lights too high, otherwise it'll look like you have your high beams on all the time.

Hope that helps,
Aj