Yay!! I found out how to use pen art! And to celebrate, I made this! Press space to pick up and lower the pen. It is controlled by the target thingy, the center of the target is the precise controller. Also, I know drawing around the thumbnail is cool, but if you want to switch backdrops, press the right arrow key. -Panda ~Update log~ 12-28-15 Now the pen changes color. More backdrop colors.
I got a book about Scratch for Christmas and one of the chapters includes info about pen art. The book is called Learn to Program with Scratch, by Majed Marji.