You want to change your profile picture in your Profile page, Kindly follow the steps below:
1. Login to https://outlook.live.com, using your existing user name and password. You will be on Outlook home page. The left side of the page highlights your email options, and the right side details your profile. Click on your user name, you will see set of options.
2. Click on "View Profile."
3. Click "add a photo" .
4. And select the picture you want to be your profile picture.
5. Click "Save".