When adding a post - roll down to the bottom of the message box and on down into the Instant UBB Code selection "buttons" below (beside the Smiley's) . On the bottom of the left column is one marked "IMAGE" Click on that, and then copy and paste the "Direct" link from photobucket into the pop-up telling you to enter the URL code for the image you wish to display (You have to have pop-ups allowed). Make sure you overwrite the original http:// that is in the box by default.
Second method is to just type '
' but without the single quotes and paste the link from Photobucket (or whichever web image host) between the two inner brackets.
Third method is to copy the IMG code from Photobucket (fourth one down) and paste that directly in the message box.