By setting up MFA, you add an extra layer of security to your Microsoft 365 account sign-in. Microsoft recommends using the Microsoft Authenticator App, but you can choose to register a cell phone number by clicking the “I want to setup a different method” link.
The first time you login, you will be prompted to provide more information to keep your account secure.
Click Next.
Click I want to set up a different method.
Select Phone and click Confirm.
Enter your cell Phone # and click Next.
Enter the verification code received and click Next.
The system should confirm your registration, click Next.
Click Done to complete the registration.