Its pretty simple. Just draw inside the frame and you can use the variables to adjust brightness or change color. Press the down arrow or S button to hide the variables and the up arrow or W button to show the variables. I added an eraser. Just set it to 50 or higher to erase and anything less to draw again.
Let me know what else to add to this. This project helped: https://scratch.mit.edu/projects/393098078/editor/
