Put your cursor over the photobucket picture and the addresses should show below the picture. Move the cursor down to the bottom line, then highlight it by left clicking on it, then right click and 'copy'. Go to your post in whatever thread, then left click to put the cursor where you want it, above or below your text, then right click & 'paste'. The picture will show in the 'preview' window before you paste your post it to the thread.
I usually bring up my photobucket album in one window, the site I'm posting to in another. I haven't tried dragging, but even that might work- don't know, just a thought. 2 small windows, one for photobucket on one side, nitroexpress forum on the other makes for easy transfer, so no back-traveling between sites is necessary.