draw what you want to draw... click the color you want on the paint wheel click the eraser to erase hold down while erasing or it'll go back to where it was. click the pencil button to go back to drawing. up arrow to change the size, space bar to clear
If there is a glitch i will try to fix it. Post your work on the studio, to do this take a screenshot of your piece (command shift 4) and make it into a project and post it.