Follow these steps to delete your Firefox Account:

1. Visit https://accounts.firefox.com/signin.
2. Log in to your account if you haven't already.
3. Scroll to the bottom and click the Delete button next to Delete Account.
4. Enter your password to confirm.
5. Click the red Delete Account button. Once you do this, your account will be permanently deleted.

You will return to the sign up page displaying a message saying Account deleted successfully.