Additional team and channel-related features and issues within Microsoft Teams for Education
Hi T2555,
Good day to you.
You can click the profile at right-upper of Teams client> click your picture like the screenshot below> Upload picture.
For further reference, there is the article:
The sync could need some time. If there isn't change after wait a while, I suggest you sign out and back in to check the result.
If you have anything unclear, please feel free to let us know.
Regards,
Joey