I have a chevy silverado 04 truck. How do you adjust the headlights?

The adjustment screws are underhood. Usually torx bit.

I would park on as level a surface as you can find that faces a flat dark wall. Square the vehicle to the wall and turn the lights onto high beam.

Vertical adjustment: Measure from the ground up to the center of the lamp beam. Take that measurement to the wall. Adjust the adjuster, usually marked "V" for Vertical, until the lamp shines just sllightly below the reference mark on the wall.

Horizontal adjustment: Marked "H" for Horizontal. This gets to be tricky, due to the beams spread. Generally, unless there is damage, the lamps will be nearly flush or even across the bodywork. You can stand kind of behind/beside the vehicle and sight the horizontal fairly close.

When I was kid, growing up in Alaska, I'd find a deserted road, unplug on lamp, adjust the other one on high, then plug in the unplugged lamp, unplug the adjusted lamp, and adjust the second lamp. But I wouldn't recommend doing that now! It's dangerous!

Clear as mud?