Using proper fingering when playing the piano is essential for developing good technique. That’s why it is so important that the pupil can associate the fingering numbers with the correct fingers.
Imagine holding an apple or a small ball in your hand, with all fingers. As a result all fingers are curved around the ball. Now place the fingers on the keys, each touching a key with its fingertip only (the thump makes contact with the outer side of the tip).
Do not allow the wrist to collapse, meaning that the wrist should be at least level with the keys, and never lower than the keys.