adjust headlight angle 2002 Yukon XL Denali

First off, This site is a blessing, You guys have been a big help...Now thats enough of the softy stuff!!!! Another quick and probably simple answer.. I need to adjust my headlights so the are level. I see the long thin bolt with a grooved head..Looking at it I dont want to break it by turning it the wrong way or is this not even the part to turn to allow the headlight to be raised the beam line. Do I turn it clockwise to raise or to lower beam or I'm I totally off track here?
Guys thanks again