GAH! I got it backward, I think. It's always easier to do than to describe. So-- edited--
To move point of impact down, move the rear sight down. To make it go left, move the rear sight left. And so on. There. I think I have that right now. The rest stands.
And if I still have it wrong, on the range if you adjust things and they get worse, go the other way.
Think of the fixed front sight as being a pivot; you're trying to swivel the breech end of the revolver around that pivot to get point of aim and point of impact to line up.
This assumes that you still have some downward travel in the rear sight. If not, if the rear sight is screwed all the way down already, your choices are to raise the front sight or change your loading.
Generally, the only way to raise the front sight is to build a higher sight. Sometimes you can buy a higher blade, but in a lot of cases the front sight blade or pin is welded or soldered in place. So your options there involve gunsmithing.
I haven't tried this yet, but from what I've read, to lower the point of aim by loading you want to load to a higher velocity. This means the bullet exits the barrel before the barrel has kicked up quite so high by recoil. You would do this by more powder or a lighter projectile. If you're shooting a round ball, you can't go to a lighter projectile, but varying the powder charge might work.
Also, how you grip the gun affects how high it shoots. You could try gripping it harder, holding it with your little finger wrapped around the grip vs. folded beneath the grip, that sort of thing. If you find you need a firmer hold, checkered grips might help without having to squeeze the grips so hard.