To change your avatar/siggy/name etc simply click USER CP on the toolbar underneath where you have to log in. It is at the very left of the toolbar, and then the things that you can change are listed on the left hand side, underneath where it says Control Panel.
on the top of the page, you will see a "quick links" button, press on arrow and you will see the options (edit signature, edit avatar etc). here's the snapshot for you :