300, allow me a moment.....
One moves the rear sight in the direction you wish to change the point of impact. If the shots are hitting left, move rear sight right. Your 686 has adjustable sights. The screw on the right hand side of the sight assembly should be turned clockwise to move bullet impact right. The screw on top adjusts elevation. Clockwise is down.
Examine your target and groups. If the groups are round, and uniformly filled, your are doing what you should be doing. If the groups are oval in shape, either horizontal, vertical or diagonal, your technique requires refining.
Presuming groups are round as appropriate, if they are not centered on your aim point, then move the sights.
A word of caution: Any expert may shoot better than you, but they may or may not shoot to the same point of aim as you. Pay attention to their shooting tips, but adjust your own sights. Any knowledgable shooter will tell you as much.
Do not expect one setting to work for all loads and bullet weights. Bullet weight will change elevation, and sometimes windage too.
Much practise will make it simpler. Mr. Mallard's suggestion of mild action work and grips that fit you are very appropriate.