Go into Photobucket and choose an album that has the photo you want to show
(in Chrome I open another tab so I can switch back and forth).
When you point at the picture with your cursor a menu will appear underneath.
Click on the box next to direct link, it will say copied.
Go back to the page you want the picture on and poke the little "Insert Image" button.
Paste the link into the space between the [img] ["/"img].
Save the message and your picture will be in it.