Well, it depends on the type of sights. For open sights(no scope) if the bullet hits to le left of where you are aiming, move the rear sight to the right. If the bullet hits high, move the rear sight down. If you have a scope, when the bullet hits left, use a coin to twist the knob on the side of the scope clockwise and if its hitting high, twist the knob counter-clockwise.
adjust rear sight up for distance
Depends on the firearm.
By drifting the front sight
Via the screw.
Fire one round, note strike, adjust sight to that point, fire again, repeat.
The owner's manual has instructions.
adjust the sight it might be broken
You sight it to a specific range , e.g. 100 meters. Clamp the rifle to a solid object, or use a benchrest. Shoot at a target and adjust the sight accordingly, until the holes in the target zero in to the sight.
Best left to a gunsmith
To adjust the rear sight on a HK G3, first, ensure the rifle is unloaded and safe. The rear sight is typically adjustable for windage by loosening the screw and moving the sight left or right as needed. For elevation adjustments, you can raise or lower the sight by turning the elevation knob. Once adjusted, make sure to tighten any screws to secure the settings before firing.
To adjust the sights so that they are aligned with the spot that the bullet hits.
To adjust the sights so that they are aligned with the spot that the bullet hits.