Rest your rifle on a sturdy surface or bipod.
Choose your distance, put some white card at that distance, then use the allen keys to adjust the laser while looking down the scope.
Because they are usually adjusted with three screws, they take a little bit more efforet than an optical scope, but once fixed they hardly ever loose Zero. If its only two screws then its just like an optical scope but a lot more fiddly!
Try zeroing one on a handgun, now that takes time!
Phantom