If you have an account already, simply reset your password in the login screen of the new MyTaxFlow, after that you need to provide your email address (known in the system) and after that you will receive an email that allows you to set a password

If you don't have an account you need to get this first, you can request a new account via your account manager, email to support@mytaxflow.com or simply create a helpdesk ticket via this link