Up arrow key is used for "Pen Up" action and down arrow is used for "Pen Down." Click the colors on the bottom right corner to change the pencil color and use 1, 2, 3, 4 to change the pencil size. Space to clear. To save your art, take a screenshot. Mac: Command + Shift + 4 (Plus sign will appear as cursor. now you can select area of drawing. It should make a camera shutter sound then the screenshot will be saved on your desktop! PC (Windows): Print Screen. (I have no idea though it's just my guess. You should probably also crop it)
I made this myself! :D