Step 1: Go to aka.ms/mfasetup (NOTE: You can skip this step if you have already assigned a mobile number to your account during setup)
Step 2: Click here to download Microsoft Authenticator or Open the Google Play Store
Step 3: Click on the the search bar
Step 4: Type 'Microsoft Authenticator' in the search bar
Step 5: Click 'Install'
Step 6: Once downloaded, click 'Open'
Step 7: Click 'I Agree'
Step 8: Click on 'Add work or school account'
Step 9: Enter your Work email address (e.g. bob.willer@domain.com)
Step 10: Enter your Work password that is linked with your Work email address
Step 11: Enter the Code that has been sent to your phone (NOTE: If you do not see this screen, please go to aka.ms/mfasetup to add your phone number. once you have done that go back to step 8.)
Step 12: Click 'Finish'
You have now setup Microsoft Authenticator for Android. Next time you login to a new device you will be prompted on your phone to approve the sign-in.