I merged your 2 threads together.
The signature box is located under Profile -> Forum Profile -> Signature
You can put text into it, or images. Images must be uploaded online somewhere (like Photobucket), then you copy the Image's URL, paste it into the Signature box, and put the visitors can't see pics , please
register or
login tags around it. Photobucket usually has the IMG code already for you under the image, just need to copy and paste.