If I understand correctly, you want to put an image on your signature right?
If that is the case you need the link to the picture itself. Then you go to the UserCP, located in the upward left corner of the main tool bar of the forum, then you select "edit signature". There you'll see a text box where you can write your signature. To put an image you just need to put the link to the picture between these tags [img ] Link to picture [/img] (remove the space from the first tag). Note however, that images in signatures can't be larger than 600x150 pixels otherwise you are breaking the signature rules and may be infracted.