Centre the rear sight for elevation and windage so that you can have a starting point. Fire three shots from 25-40 yards to establish. If all three shots hit in 2″-3″ area, then move the sight right or left and up or down if required. Do not adjust your view until you are hitting all the shots in the group.
Move the sight to the left, if the shots are hitting the target at right. If the shots are hitting at the left, move the sight right. If the shots are high, move your sight down. Similarly, if the shots are too low, adjust your sight up.