How do I zero a scope on an airgun?

Mount the scope properly, level it, and rough-zero at 10 to 15 yards (a near zero) using a large backstop.

Then move out to your intended primary distance: 20 to 25 yards for indoor work, 30 yards as a versatile general zero, or 35 to 50 yards for hunting. Shoot a 3- or 5-shot group, adjust windage and elevation toward the group, and repeat until the group sits on the bullseye. Common turret values are 1/4 inch per click at 100 yards, which is roughly 1/16 inch at 25 yards.