To set up the Microsoft Authenticator app
Sign in to your work or school account and then go to your https://myprofile.microsoft.com/page.
Select Security info from the left navigation pane or from the link in the Security info block, and then select Add method from the Security info page.
On the Add a method page, select Authenticator app from the drop-down list, and then select Add.
On the Start by getting the app page, select Download now to download and install the Microsoft Authenticator app on your mobile device, and then select Next.
If you want to use an authenticator app other than the Microsoft Authenticator app, select the I want to use a different authenticator app link.
If your organization lets you choose a different method besides the authenticator app, you can select the I want to set up a different method link.
Remain on the Set up your account page while you set up the Microsoft Authenticator app on your mobile device.
Open the Microsoft Authenticator app, select to allow notifications (if prompted), select Add account from the Customize and control icon on the upper-right, and then select Work or school account.
If this is the first time you're setting up the Microsoft Authenticator app, you might receive a prompt asking whether to allow the app to access your camera (iOS) or to allow the app to take pictures and record video (Android). You must select Allow so the authenticator app can access your camera to take a picture of the QR code in the next step. If you don't allow the camera, you can still set up the authenticator app, but you'll need to add the code information manually.
Return to the Set up your account page on your computer, and then select Next.
The Scan the QR code page appears.
Scan the provided code with the Microsoft Authenticator app QR code reader, which appeared on your mobile device after you created your work or school account in Step 6.
The authenticator app should successfully add your work or school account without requiring any additional information from you. However, if the QR code reader can't read the code, you can select the Can't scan the QR code link and manually enter the code and URL into the Microsoft Authenticator app.
Select Next on the Scan the QR code page on your computer.
A notification is sent to the Microsoft Authenticator app on your mobile device, to test your account.
Approve the notification in the Microsoft Authenticator app, and then select Next.
Your security info is updated to use the Microsoft Authenticator app by default to verify your identity when using two-step verification or password reset.