The bore is in a straight line.
The laser shows a visible extension of that line.
Your optic is mounted a fixed distance from the bore.
Mark a piece of paper with 2 points the same distance as between the bore and the optic.
Mount the rifle so it doesn't move.
Place the peice of paper so the lower point is in line with the laser light.
Adjust the reticle of your optic until it is on the upper mark.
Turn off the laser and remove it from the bore. Clear all obstructions from the bore
Go to the range and zero the optic.