If your scope model is equipped with an adjustable objective lens mount for a parallax correction, rotate the focusing ring to the appropriate standard-parallax setting. Sight through the bore at a target of 100 yards. Move the rifle about to center the target in the bore. Sight through the scope and adjust the windage and elevation screws to center the target on the reticle. Never force the windage and elevation screws past their natural stop.
Internal damage can result rendering the scope inoperative.
Since final zeroing involves live fire, check bore to be sure it is free of any obstructions before loading. Use eye and ear protection. Fire three rounds at your target. Note impact on target. Measure the distance from group center to target center.