Super easy to do but just be gentle. If you have your 100m zero set on your rifle then you remove the indicator cap to expose the clutch/zero stop systyem. The newer ones have 4 screws holding the upper clutch in place. Loosen those screws 1-1.5 turns and then turn the upper clutch clockwise until it makes contact with the lower clutch. Back it off counter-clockwise about 1/4 turn and you should be pretty close. Tighten everything back down.
Make sure you only tighten those 4 clutch screws to 2 in/lbs or you will lock up that clutch for future adjustments.
Otherwise phlegm's technique is the other easy way to do it.