You will need both your desktop/laptop computer as well as your primary mobile phone to complete these steps.
Starting with your Mobile Phone
1.Download the Microsoft Authenticator app:
FOR IPHONE USERS: Click here: https://apps.apple.com/app/microsoft-authenticator/id983156458 or search for and click on Microsoft Authenticator in the App Store then install it.
FOR ANDROID USERS: Click here: https://play.google.com/store/apps/details?id=com.azure.authenticator or search for and click on Microsoft Authenticator then install it.
2. After installation, Open Microsoft Authenticator
3. Allow notifications if/when requested
4.Click SKIP
5.Click Ok
6. Click Add Account.
You may need to do this in the top right via the + button (iPhone) or the three dots then add account (Android)
7. Click: Work or school account
8. Allow Camera access if/when requested
9. Click Scan QR code
10. You should now see a camera window on your phone.
Keep that open, then continue the steps you started on your laptop.
FROM YOUR DESKTOP OR LAPTOP
11. Click here: https://aka.ms/MFASetup
12. If asked Enter your work email address or click on the saved one
Click Next
13. Enter your work email password, Click Sign-in
14. If asked to Update your password.
Enter your CURRENT work email password
Enter a NEW password twice
Click Sign in
15. Click Next
16. Click Next
17. Click Next
18. DO NOT CLICK NEXT AT THIS SCREEN
Move on to the next step on your Phone.
BACK ON YOUR PHONE
19. Hold your phone up to your laptop screen and place the QR code in the window. Wait for the window to close before moving on to the next step.
BACK TO YOUR DESKTOP OR LAPTOP
20. Click next
21. You will see a number on your computer screen.
BACK TO YOUR IPHONE
22. Enter the same number you see on your computer screen then click Yes.
BACK TO YOUR DESKTOP OR LAPTOP
23. Click Next
You have now successfully set up Multi-factor Authentication of your Office 365 account.
Quit and re-open all Office apps you currently have open (Outlook, OneDrive, etc). At the re-login request, simply enter your password, then approve the sign-in from the notification on your phone and check "Save for 90 days" if that option is available.