These instructions are designed for those that have completed the multi-factor authentication (MFA) and self-service password reset (SSPR) setup. If you have not completed that setup, please refer to the Knowledge Base article Microsoft MFA and SSPR – First Time Setup.
If you would like to change your default MFA sign-in method:
It is recommended to set your default to "Microsoft Authenticator - notification" due to its convenience and enhanced security.