If you decide to delete your account, you have to:
1. Go to the "More" tab.
2. Tap on the "Delete Account" menu option.
3. Tap the "Delete" button.
Note: If you delete your account, you will delete all the data, progress, and other personal info. You can delete your account only if you are a registered user. If you want just to sign out, you can do it from the Stats tab.