Instructions
1) Sign in to microsoft365.com.
2) In the upper right-hand corner, click your profile icon (avatar).
3) Click the camera icon.
4) Click Upload a new photo.
5) Click on the photo that you want and click Open.
6) Click Set as profile photo.
NOTE: The photo that you upload cannot be larger than 100 KB, and the photo should use any of the following extensions: ".jpg", ".gif", ".png", or ".bmp".
Outcome
Your profile photo will be changed in Microsoft 365. This will be your profile photo whenever you are using an online Office application.