Welcome!
I wrote this up on Wiki but apparently they banned "how-tos" so its in the discussion.
In order to adjust the point of impact to coincide with the point of aim, a 3-mm hex wrench is required. On the MC-10-80, there are two points of adjustment. The front (windage) allen screw holds down an adjustment screw. Loosen the allen screw and turn the adjustment screw CLOCKWISE to move the point of impact LEFT. Afterwards, tighten the allen screw and verify that the point of impact has been adjusted. Repeat this procedure for the rear adjustment (elevation). Turn the adjustment screw CLOCKWISE to move the point of impact UP. Proceed to zero out the sight at 50 yards using a nose-to-receiver cheek weld. The use of threadlocker on the threads of the allen set screws is not recommended. The adjustments are very coarse and should only be done in small increments to keep the shots on target.
When aiming at a target, the center 1 MOA dot of the daytime reticule should be your point of impact at 50 yards. If this is not the case, adjust the sight according to the instructions above and repeat the procedure until the point of impact coincides with the point of aim at 50 yards.
Remember to loosen both screws when adjusting to prevent binding.
Do NOT bother buying the $50 adjustment tool, it's a total waste of money. If anything, it should have been included FREE OF CHARGE with the PS90.