How do I mount a scope on an airgun correctly?

Use airgun-rated rings on a matching dovetail (11mm) or Picatinny base.

On springers, use a scope stop pin or a stop block to prevent the rings from creeping forward under recoil; many airgun bases have a stop hole drilled in the receiver for this. Tighten ring screws evenly in increments, just snug at first. Set eye relief by shouldering the gun naturally and sliding the scope forward and back. Level the reticle to the gun's vertical axis. Tighten everything to spec, not gorilla-tight.