Tougher than it looks, the compact RST works on several pistol makes and models.
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
Veteran competitors in all shooting disciplines have long since memorized their sight adjustments. For the rest of us, here is a quick review.
Figure out the number of clicks per ring to estimate needed correction.