In your PhotoBucket albums are "thumbnails" of the actual image.  Check the box for the image you want to post.  Click the Generate HTML and IMG code button.  This will open a window with code for all sorts of image boards and such. 

You can use one of the first two:

"HTML clickable thumbnails for Ebay, LiveJournal, MySpace, etc."

                                     OR

"HTML images for Ebay, LiveJournal, MySpace, etc."

The only difference of the two is that the first option will only post a thumbnail to the site but it is clickable so that the visitor can get to the full size version.  This is ideal when you think your image might be to big to post outright.  The second option will post the full size version on the board. 

Once you choose which one you want to use, copy the code in the box and just simply paste into your post.  No need to type the tags that I have at the top of the signing page because they are already built into the code that PhotoBucket provides.