Try this! Just hit the tiny picture of the mountains and the sun on the bar that is above the area that is above your post. Once a window pops up, all you need to do is insert a valid image URL and hit OK.
Otherwise, you can just use this.
[img]URL goes here[/img]
Otherwise, you can just use this.
[img]URL goes here[/img]
![[+]](images/collapse_collapsed.png "[+]")