One of the most important factors in putting is alignment. If you’re confident your ball and clubface are lined up with the read you’ve chosen, it will free up your stroke. This leads to the next important factor in putting which is consistently making the impact with the center of the ball.
If you want to roll your ball on the correct line you need to aim your putter face where you want the ball to start. To do this it helps to align your eyes square to the putter face and the starting line.