Step 11: Aim your Lasers
"The Y galvo should be positioned with its mirror pivot running horizontally, and the mirror oriented down.
The X galvo should be positioned with its mirror pivot running vertically, and the mirror oriented towards your left.
The laser should be pointed at the mirror of the Y galvo.
The Y galvo should be angled so the laser bounces of its mirror onto the X galvo's mirror.
The X galvo's mirror should be pointed toward where you want the laser show to project."
If my image isn't clear enough, I recommend checking out theirs as well.