Hi Kibo,
Go to "My Profile" click on "Edit Avatar" and enter either the addy to the pic you wish to use or upload one from your computer. Keep in mind that the size of the pic is very important...if it is too big, it will not take the pic and display it. Pics need to be 80X80 pixels or 19.5kb whichever is smaller in order to work.
Hope this helps!

sabby