Just go to your User Control Panel, (upper left) click on Profile. Now you can add a signature with a web link if you choose (click on Edit Signature).
If you want to add an avatar image, simply find one you like, and go to this link to resize: http://www.resizeyourimage.com/
Simply change your image to 90 width x 90 height and save. The directions on the website are clear and easy.
Now go to Edit Avatar in your profile menu, browse and upload your image. You are done!
