Click on your Blue dot with the T in the middle...top right of the screen. Then click on your round Blue T on the left. This will allow you to edit a picture (upload a picture) into your profile picture.
That picture is referred to as your "avatar".
As in the question, How would I change my avatar?
Or the complaint, "I can't change my avatar picture"
Or in the complement, "My that's a lovely avatar that you're displaying."