How to adjust headlight height:
Pop off the long black plastic pieces on either side of the frunk (they just lift off - push down on the rubber circles on either side to get them through the holes). They need to be pulled away from the frunk as to the side of the car they have a lip that goes under the frunk edge. (Trust me, if I can do this as mechanically uninclined as I am, so can you). Important: leave them off until you're fully satisfied with your headlight height, including through a test drive.
Underneath that, about a third of the way up the hood on both sides of the car (near the outer edge, under the lip), is a white plastic socket that is designed for a 6mm allen wrench. Insert wrench and turn - one way aims the headlight up (I forget which), the other goes down. You probably want to turn them the same amount on each side, so keep track of it.
I found it very hard while parked to get the headlight height exactly right (small variations in height get magnified with distance and most people - including the Tesla service center in my experience - don't have a perfectly level garage floor). I found the best option was to iterate changing the height with a brief test drive until I was satisfied.
When done, pop the two side pieces back on - putting the lip under the edge of the side of the frunk first and then gently but firmly pushing down on the plastic pieces to lock them in. You need to bend and pull the rubber circle through the hole (reverse of what you did to get them off).
QED