Your profile picture is located inside of your Member App account and is used as a default when you create a new membership. When you change your profile picture in account settings it will become the new default details that will be populated on the setup step when you create a new membership.
Once you've done that you can hover your mouse overtop of the current profile picture and you'll see a camera icon appear. Click overtop of this image:
Once you've done that you can now navigate through your files and select a new profile picture.
Once you've selected your new profile, click 'Open' to start profile image upload. After the the image has been uploaded to our server, you will see a new profile image appear on the account settings page.