1. Go to https://aka.ms/MFASetup in a web browser.
2. Sign in with your work email address and password. When you get to the following page (if you haven't already signed up for the app or registered your phone number), choose I want to setup a different method in the bottom left-hand corner of the page.
3. In the window that appears, choose Phone from the drop-down list. Click Confirm to confirm your choice.
4. Type in the mobile phone number that you wish to register, and choose the Text me a code option and click Next.
5. Microsoft MFA will send an authentication text code to the telephone number you have provided. Please check your mobile phone for the authentication text code. Enter the text code received into the textbox provided and select Next to proceed.
(If you do not receive a code, check the number you gave by clicking Back and verifying the number before trying the Resend code function)
6. You have successfully registered your phone number for authenticating using text message, select Next to finish the registration process.