if you're talking about the signature .. do this
1. Click on your username and look for MY PROFILE and click on that.
2. Once in MY PROFILE, click on EDIT MY PROFILE on the right middle corner.
3. Once in EDIT MY PROFILE, click on CHANGE SIGNATURE on the left navigation bar.
4. Once in CHANGE SIGNATURE, type in the code : [IMG ]URL OF PICTURE - CAN BE HOST IN TINYPIC.COM[/img ] <-- don't forget to take the space between the IMG ] attribute.
5. Once done with coding, click on SAVE CHANGES.
You should be done by then. Hope this helps and that it is what you're looking for too.
*note: you can do the same for the avatar as well. (id picture)