Southpaw
The simplest way is to tighten the rings to the point you can turn the scope with a moderate amount of effort. You the hold the gun out in shooting position with a straight line, which can be either horizontal or verticle, in the field of view and use that as a reference. This, especially a vertical line suchas a door frame, will give a reference for the gun and the crosshairs. When it looks right, tighten the ring screws about 1/2 turn at a time alternating side to side, it should stay straight this way. Note that you only need to do this with one ring, and when it is snug it will hold the scope while the screws for the second ring are tightened.
If the rings are Weaver type, you want to make the initial tightening sufficient so you can only turn thr scope with some difficulty. This minimizes the amount the ring cap can turn the scope as the screws are tightened.
Remember, perfect is not necessary, only aesthetically pleasing! If the crosshairs are vertical when you hold the gun in a comfortable fashion for you that is close enough.
The simplest way is to tighten the rings to the point you can turn the scope with a moderate amount of effort. You the hold the gun out in shooting position with a straight line, which can be either horizontal or verticle, in the field of view and use that as a reference. This, especially a vertical line suchas a door frame, will give a reference for the gun and the crosshairs. When it looks right, tighten the ring screws about 1/2 turn at a time alternating side to side, it should stay straight this way. Note that you only need to do this with one ring, and when it is snug it will hold the scope while the screws for the second ring are tightened.
If the rings are Weaver type, you want to make the initial tightening sufficient so you can only turn thr scope with some difficulty. This minimizes the amount the ring cap can turn the scope as the screws are tightened.
Remember, perfect is not necessary, only aesthetically pleasing! If the crosshairs are vertical when you hold the gun in a comfortable fashion for you that is close enough.