The code it gave you "[img ]" has to be used in your signature box.
Have you seen this icon?
On the posting page, if you look to the right of the "Instant Graemlins", you'll see "Instant UBBCode". Below that you'll see that icon. You can click on that icon and you'll get a window that allows you to paste your url. When you click "OK", the posting software will add the necessary codes.
This is a very easy way to add pixs to your posts.