Sean,
As David said, use it going forward. If you cant get it to work as David got it to work for your picture, then start a post by using a "Quote" of David's post of your picture. You'll see the codes in the quoted part and you can use that format.
If your issue is that your picture isn't as large as you want it when you do click through, it's because when you upload your images to Photobucket it automatically compresses them to 1024x768 pixels. You can change your upload options to save a larger picture, say 1600x1200. You can click on the options on the right side of the screen on the first bar:
Upload to Photobucket Customize your upload options
Whatever size picture you uploaded will be displayed on the click through.