This doesn't belong in this section, and the answer to this question belongs in the "Help Guide" section. In any case, go to "Settings" and "Change Avatar". Upload an image from your computer, or pick a default image. Hope this answers your question.
It has lots of useful info and topics on how to do things with your account / profile on TamaTalk - including "How to show a picture (Avatar) by your posts" and "How to show a poem or message below your posts (signature)".
I will just close this topic for now - but if you have any more problems and you can't find the answers in the Help forums or in the Users Guide to TamaTalk feel free to PM one of the Staff for help or any of the friendly members here