From your album page in photobucket, click on the picture you'd like to insert into a thread. Once that loads, you'll see a little chain link near the top. Select that chain link and a window will open. That window will say "photo links" on the right side. Click on the one that says "IMG" and it'll load the link into your clipboard. You can then paste that link into your thread post and your picture will be inserted into the post.