Making putts requires that the face of the putter is square to the intended target line at the moment of contact with the ball. Good putters accomplish this by maintaining a triangle between the arms and shoulders throughout the stroke. Many problems in putting are because of excessive movement in the head or upper body during the stroke, which cause the face of the putter to get off line at impact.
To improve your contact with the ball, work on building a stroke that is controlled by the shoulders. To work on this pendulum type stroke, place your palms together in a downward prayer position. Notice how you have formed a triangle between your hands, arms and shoulders. Now make a stroke maintaining that triangle and keeping your head and lower body still. As you rock your shoulders, your left shoulder should work slightly down on the backstroke and slightly upward on the forward stroke. This will help to keep the face of the putter on line at the impact position.
Work on this and start making more putts.