http://j4dhkkrfv66no3miwc7dv22cytk4rcjlsv6yqsjxgcnkswxqlbjuh2qd.onion/en/faq
In order to reset your password, you need to have security questions and/or a recovery email set up. If this is the case, then go here and click on 'Forgotten password'. If you haven't set any of these options, then there's nothing else you can do, but register a new account.