To install the Microsoft Authenticator, first locate it in your phone's app store. 

• Google/Android: https://play.google.com/store/apps/details?id=com.azure.authenticator
• iOS/Apple: https://apps.apple.com/us/app/microsoft-authenticator/id983156458

There are some similarly named apps available, so make sure to confirm that the developer is the Microsoft Corporation. It should look something like this:

Click Install and allow the app to download and install. Once complete, open the app and accept the security and privacy policies. You will then be asked to either to sign in to your account, add a work or school account, or scan a QR code. 

Select "Add work of school account" to continue. 

Sign in with your school account, using the same email address and password you use to access the class portal. Once you enter your password, you will be asked to authenticate using your currently active method. After authenticating, your account will be added. You can check your settings by clicking the account in the app.

If you want to change your authentication method, or switch between using a push notification or a one-time password that changes every 30 seconds, you can go here: https://mysignins.microsoft.com/security-info

The Notification method sends a push notification to your phone. You will then select Approve or Deny. Only press Approve if you are actively trying to log in. You may also need to input a code from the sign-in screen where you are attempting to log in. The Hardware Token - Code option is a one-time password that will require you to open Authenticator app, select the account, and input the password as if it it were sent by text. You may switch between these options as often as you like by going to the link above.