Howdy
Bring plenty of ammo with you.
Set up a target at whatever range you want, whatever distance you would like to zero the gun to.
Place your target on top of a much bigger piece of paper. This is so if the sights are way off and you completely miss the target you will still have an idea of where the gun is hitting.
I like to rest the grip of a revolver, not the barrel, on sand bags. But that's the way I shoot, it does not really matter.
It's good to put one of those bright florescent stickies on the center of the bulls eye, so you can see the target real well. Decide how you want the gun to shoot. I like to hold at six o'clock on the target so I can see the whole target. If you want the bullets to hit exactly on top of the front sight, that is good too.
Fire groups of at least three shots, five is better. Circle the group and determine where its center is. Move the rear sight in the direction you want the bullets to go. Raise it if you want the bullets to go higher, lower it if you want them to go lower. Same thing with windage. Move the sight to the right to push your bullets to the right and vice versa.
Your Model 19 has what is known as the Click Adjustable rear sight. You will feel a subtle click six times for every rotation of the screw. Shoot a group, then adjust the sight as needed. The biggest mistake shooters make when sighting in a firearm is not firing enough rounds. Shoot and Adjust. You will figure it out.
