You must be registered for see images
Ok so
1: click the "Insert Image" icon (yellow box with mountain)
2: paste the direct link to your image. if you get the picture from photobucket you can get the direct link easily at the right side of the page. A direct link means a web adress specifically for that picture, not a web adress whose page shows the picture somewhere on it.
If this doesn't work, your link must not be good
You must be registered for see images