Instructions
Click on one of the six eraser tools. They all have the same effect: they white-out whatever you click on. The only difference is in their size. Once you select the eraser you want, click on the undesirable region to delete it.
Select the undodog to undo your last action. If you drew a crooked line, clicking the undodog will make it go away. You can also undo erasers, in case you deleted something you want to keep.
Choose from the ten full-screen erasers. These will delete everything on the screen, though they do it with different effects. For instance, the fade effect causes the image to slowly disappear, while the warp effect causes ripples to run through the image before it's pushed off the screen.