Adjust the sights on your rifle so that your shot group are centered on the target. Including a handy table for sight changes with a BB Gun, Air Rifle or Smallbore Rifle with common paper targets
To shoot a red dot in bullseye well, you have to choose: focus either on the target or on the dot. You can’t do both, or go back and forth between the two. Here are techniques from Brian Zins to properly aim a pistol red dot sight