You will have to restore your device and set it up as a new account. I don't think setting up from a backup will work as the passcode will still be there. You could always try though, it wouldn't hurt.
Plug your device into your computer/laptop and open iTunes (The normal computer you sync with) And then click on your device in the side bar. You should see a box on the screen that says restore. Just tap that box and it will ask you if you are sure you want to restore. Click yes.