Depending on the type of keyboard you’re playing, you can either sit or stand while you play the piano. As a general rule, most pianists sit at the piano, but many rock keyboardists stand behind their keyboards.
As a beginner, start your musical endeavors in a seated position. No matter what kind of keyboard you play, sitting brings you closer to the keys and makes you more comfortable as you practice.
Whether sitting or standing, you should be comfortable at all times. Your feet should rest firmly on the floor. Your hands should have a nice relaxed arch to them. The keys should be at an appropriate height so that your hands and forearms are parallel to the ground:
Make sure your back is straight and that you aren’t slumping, slouching, or hunching over. Not sitting up straight leads to backaches — the kind that discourage you from practicing.