Explanation/Reference:
Explanation:
Box 1: Create a multi-factor authentication provider with the Per Enabled User usage model.
Box 2: Enable multi-factor authentication for all user accounts.
Box 3: Instruct users to use a mobile phone to complete the registration process.
Adding Multi-Factor Authentication to Azure Active Directory (for Office 365 users) Step 1: First we create the usage model of the MFA provider.
We should use PerEnabled User which is used for Office 365.
Note:
Per Authentication - purchasing model that charges per authentication. Typically used for scenarios

that use the Azure Multi-Factor Authentication in an application.
Per Enabled User - purchasing model that charges per enabled user. Typically used for scenarios such

as Office 365.
Step 2: Enable Multi-Factor Authentication for all your user accounts.
You need to enable multi-factor authentication on your Office 365 users.
Step 3: Have a user sign-in and complete the registration process.
The users can use their mobile phones to complete the auto-enrollment process.
Details: After being enrolled for multi-factor authentication, the next time a user signs in, they see a message asking them to set up their second authentication factor. Using the enrollment process the users will be able to specify your preferred method of verification.
The following methods exist: Mobile Phone Call, Mobile Phone Text Message, Office Phone Call, or Mobile App.