Adjust the sights in the direction you want the gun to shoot, i.e., raise the rear sight if you want to hit higher, shift it to the right if you want to shoot more to the right.
There's no set rule for how far to turn the sight to get a desired result. Trial and error's always worked well for me. If you're shooting 4" low at 10 yards, I'd suggest a 1/2 turn on the elevation screw. If that's still too low, another 1/2 turn, etc., 'til you get the desired result.
Remember a couple of things before you begin, however. First, it's often the shooter and not the gun that's causing a consistently "inaccurate" result. Are you shooting single or double action? A consistently low result in single action might be due to a flinch on your part, that is, pushing the gun down in anticipation of recoil. Just about all of us have had to deal with that issue at one time or another. The way to correct that problem is not to adjust the sights but to eliminate the flinch.
About two years ago I purchased a very nice 66 no-dash. When I first began firing it, everything and I mean everything was consistently low left. I adjusted the sights in order to "zero" them and managed to find an adjustment that put my shots more or less in the center. However, the more I fired the gun, the higher my patterns became and the more to the right I shot. I finally realized that the gun's sighting "error" was my shooting error. I centered the sights back on their original settings and now I shoot pretty much to point of aim with it. Practice makes perfect, in other words.
Finally, lighter, higher velocity ammo will shoot lower, consistently, than heavier ammo. The gun was built to shoot 158 gr. ammo. If you're shooting lighter ammo than that it may show up as consistently low groups. You can raise the sights to compensate or, you can buy some 158 gr. ammo.
