Connect the COM USB to your computer. That's the USB farther from the switch. SSH into your Edison (making sure you're using the correct settings. Check out this step in another instructable I made.) The only way to reflash the Edison is to do so before it actually boots. With the SSH terminal up, reboot the Edison. After a little, you will see (check out the image above to see it.):
Press a key to keep the Edison from going any farther. Now you will see the following:
This is a prompt. Type:
And let the Edison work. Once it's done, your Edison is fully reset, and you have a clean OS! You should feel very happy because you're done, or frustrated if you still have to restore old settings. Enjoy!