Image (Img) tags.
Click on the Img button [img]
Followed by the URL which has to end in jpg, gif, or whatever but not html, etc.
Then click on the Img button again to close the tag [/img]
The non picture showing above is where the path would be to that picture.
Do not link a pic from an outside site without permission as you are stealing (pirating) their bandwidth, which is illegal.