Press the flag once or twice, and wait for ItchyCatlll logo and stuff. Then, once the menu loads (with the "start" and "instructions" buttons as the two black keys on the bottom row of the grid), press "instructions" to see how to play, and "start" to begin playing. The instructions use the up and down arrow keys to scroll, and the back button to return to the menu.
Thanks to ItchyCatIII for: Piano Tiles (Original Project)
