You swing the club by feel, and you learn feel through good motion. Keeping your eye on your shadow will teach you the feel of your upper body staying in position - neither moving to the right or left- nor up or down.
To keep other body movements from moving the swing center keep your
weight to the inside of your feet. Never allow this weight to transfer
outside as this will pull you out of position. Allow the rotation of
the shoulders and arms to carry the club to the top of the backswing.
These are some key points that will give you feedback in understanding
how to feel the proper swing center.