Go to benutzer KM (why is it in German?
) it's the most left button of that row buttons in this window.
-->Edit profile I think (third button)
And there you can change or get an avatar (picture) You can save one from your hard disk. But it has to be small enough (if it's to big, be creative with some drawing programs or something)
You probably still don't get it but try it with this first