I would get a cheap laser that clamps onto the front of the trigger guard. It doesn't really matter if it is completely zeroed and sighted in or not, but it does have to be tight so it doesn't drift during shooting. Using your normal shooting stance/grip, concentrate on keeping the laser dot centered on the bullseye during the entire trigger squeeze. The gun should surprise you when it fires. Your goal is not necessarily to put the shots in the bullseye, but to keep the laser dot on the bullseye and shoot as tight a group as possible.
When you get the hang of that, take the laser sight off and shoot the gun exactly the same way, using the iron sights
Many new shooters make the common mistake of forcing the gun to shoot when their sights are on target because they think they have to fire before the sights drift off target. This causes you to push the gun down and pull it to the right (if you are right handed). Your gun will do a natural figure 8 around the bullseye. The trick is to start trigger squeeze as the gun drifts toward on target. With practice, the trigger will break and the gun will fire as the sights cross the bullseye. During the trigger squeeze, if your gun drifts off target, hold the trigger right where it is, and as the gun comes around to back on target, start squeezing more. The goal is not to force the gun to fire while on target. The goal is to let the gun fire on it's own, without disturbing the sight picture, and with practice, to time it correctly.
Also, the longer you hold the gun out in front of you in the firing position, and hold your breath, the more it will drift. If you have to, just lower the gun, take a couple deep breaths, bring the gun up and start the process again.
