Step 1: Sign in to your Office 365 portal or Outlook on the web using the below URLs.
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http://portal.office.com
http://outlook.office.com
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Step 2: Click your user photo on the right side of your name.
Step 3: In the My accounts window, click your user photo.
Step 4: From the new Account Information window, click ‘Browse’ to select and upload your photo.
Step 5: Click Save to set your user photo.