1. Set a target 15-25 yards away from you.
2. Aim at the center.
3. Shoot
4. If you are not on the bullseye, then adjust your rear sight accordingly. Move your rear sight in the SAME direction as the direction you want the new point of impact to move toward. Right makes your POI move right, Up, Up, Left, left, and Down, down.
5. Repeat steps 3 & 4 until you are on the bullseye.
Consult your owners manual or ask again here, for the proper sight picture with iron sights. Most people use a 6 o'clock hold.
Be careful. Follow the 4 rules to the letter. Have fun.