Hand Position
The correct hand position at the beginning may seem one of the least important things, but in many ways it is the most important.
When we place the fingers on the keys we do no line the fingers up so they are all playing on the edge of the white keys as this makes the fingers unevenly curved and the wrist tight. It is unnatural and the tension is not recommended.
Align third finger with the arm, which is the most natural position, there should be no awkward or extreme angles.
Start by letting the arm drop loosely by the side, as if it is handing from the shoulder. Do nothing! Notice how it feels, the length of the arm the relaxed feeling of the hand. This feeling brings blood, oxygen and energy to the hand. Imagine yoru hand is like a hot air balloon When the arm hands loosely at the side the forearm naturally lines up to the third or fourth finger.
Posture
There are many ways to sit to play your instrument, some look great, some a creative, some are questionable and some bring out the showman in you.
For exam purposes, and to play in a professional pianist way, there is an official way. This will make it easier for you to play correctly.