https://www.microsoft.com/en-us/security/mobile-authenticator-app
Before you can use the Microsoft Authenticator app, you must:
Download and install the Microsoft Authenticator app. If you haven't done this yet, see Download and install the app.
Add your work/school account (e.g. someperson@pgst.nsn.us) by scanning a QR Code, do the following: On your computer, go to https://office.com and sign in. On the Additional security verification page.
Select the checkbox next to Authenticator app, and then select Configure.
5. On your phone, open the Authenticator app, select the plus icon and select Add account, and then select Work or school account, followed by Scan a QR Code. If you don't have an account set up in the Authenticator app, you'll see a large blue button that says Add account. Note: Please allow push notifications
6. During the login process you enter your password. On the left is on your laptop, workstation or web browser. On the right, your phone will display the Microsoft Authenticator app.