The way I do it is:
Once I upload the photo to Photobucket, on the right of Photobucket there is a box "Links to share this photo"
Copy the direct link and paste them in here like you have done above.
Then just hightlight a full link and click the icon insert image above.
it will add the IMG code to your link (without the spaces)
[ img]your link[ /img]
And thats you done. Just click preview before you submit your post to see if you have did it correctly.