Whoops, I think I added a comment instead of answering, and I'm not sure how notifications work on here, so I'll just add what I said as an answer as well. When you click your picture/username, it takes you to a page that has a "settings" button at the top (under the main grey header bar, to the left of the logout button). If you click that, it will take you to a page that has an option to upload a profile picture (the third option down).
You can also just go to https://www.nihongomaster.com/myaccount/settings to get to the page with the option to upload a pic.Turtle
Commented 3 years ago