You can click the notes on the screen or you can press the following letters on your key board, c, d, e, f, g, a, b, 2 (2 is for C on the right). When you're on the menu, you can select 'Songs' to see a list of songs, if you click on a song it will show the notes, so that you can play along! Or, you can click 'Free Play' to play a song of your choice!
This was for a presentation in music class. Really sorry if some of the notes are wrong.