Set-up Two-Factor Authentication. It is recommended that you use Authy, Google Authenticator, or Salesforce Authenticator to enable Two-Factor Authentication.
Once you have enabled this step, you may add backup method if you are unable to authenticate via authenticator app. There are two backup authentication methods, Scratch Code and SMS. You can enable both of them as the backup method.
For the Scratch Code, you will be given several codes. You need to store these code somewhere safe. Each Scratch Code can only be used once.
For SMS, you will receive an SMS code to your mobile phone to verify your account.
If you are logging in using the backup method, the Two-Factor Authentication will be disabled after that and will need to be setup again.
In order to update your account with a new passowrd, you need to provide your old password. If you are registered through GitHub, DigitalOcean, or Google authentication, you need to reset your password.