- Sign in to Office 365 using your password and verification code.
- Choose Settings > Office 365.
- Choose Security & Privacy > Additional security verification.
- Choose Update my phone numbers used for account security. This will display the following page:
5. You have options to select Text code to my authentication phone.
Note: Microsoft has moved additional security verification page from Office.com website. However, you can access it from this link:
Please review this step by step video: