Well the first thing you need to know about piano is sheet music. You need to develop a strong learning of how to read music, and how each note corresponds to the key son the piano.
You need to learn the keys on the piano. Basic stuff.
You need to look up which notes can be played by which fingers. Usually, beginners music will give you numbers, here is what they mean.
They go from 1 to 5, starting on your thumb from right to left, for each separate hand. So on your right, your thumb is 1, pointer finger 2, middle finger 3, and so on.
If you develop a strong sense of which finger goes where, you can start to make little exercises for yourself. Keep them simple, and repeat them, over and over again. If you get it right at least 6 times in a row, move on to the next area.
Piano is one of the easiest instruments to comprehend note wise because it is laid out before you. It is easy to see half steps, whole steps and just how many notes you need to go up. All you have to do is count them.
About the music, right hand is the top, g clef, and the left hand is f clef, the bottom part (as seen on the music)
There is so much more to know about piano, if you need any tips or pointers, just message me, I will be willing to help.