You will be met with a title screen. Click it to hide it and get into the game. To draw, hold down on your trackpad and move, right click with you mouse and move, or move your finger or stylus on your screen or trackpad. Click the E key or click the green flag to erase your screen. Click the U key to hide the variables on your screen, and click the I key to show them again. Change the position of the hue slider to change the color of your pen, change the position of the saturation slider to change the saturation of the pen, and change the position of the value slider to change how light or dark your pen is.
Thanks to @wantsomesteakies for the original project Untitled Drawing Game https://scratch.mit.edu/projects/1071670092 .