Do you have a Photobucket account? Imageshack works too but I tend to use PB. You can also use your DrunkDuck account to host images but PB has all the tags written out for you.
When you add an image to the forums and the image is hosted elsewhere, you're hotlinking. To add an image to this particular forum, you need to use the IMG tag.
Edit: I can't seem to get the code tag working but to see the IMG tag, just quote this reply. (To quote this reply, look at the upper right hand corner of my post. You should see a link that says "quote." This allows you to quote me when you're replying. It would also show the IMG tag.