With multi-factor authentication, every sign-in is also confirmed on your smartphone. You need a computer and a smartphone.
Steps
On your computer, open aka.ms/mfasetup and sign in with your company account.
Choose Add sign-in method › Microsoft Authenticator.
On your smartphone, install the Microsoft Authenticator app: App Store (iPhone) or Google Play (Android)
On your computer, click Next until a QR code appears.
In the app, tap + › Work or school account › Scan QR code and scan the QR code on your computer.
On your computer, click Next and approve the test request in the app. If a number is shown, enter it in the app.
Important: Only install the Microsoft Authenticator app published by Microsoft. There are fake apps with similar names.
Note: If no request arrives in the app, check that notifications are allowed for Microsoft Authenticator. When changing smartphones, use “Transfer Microsoft Authenticator to a new smartphone”.
More information: Use Microsoft Authenticator with Microsoft 365