Your computers temporary storage which you can copy addresses into and then paste somewhere else can only hold one address at a time.
If you click the share link and then copied the "IMG" address for more than one picture your computer will erase the previous pictures address and copy the latest address.
If you want to post several different pictures, keep the Photobucket site open in one of your browser tabs and the MLF site open in another tab.
Then, copy the Photobucket IMG for one picture, come back to the MLF and paste it into your post. Then, go back to the PB site and copy the IMG of the next picture. Come back to the MLF and paste the new pictures address into your post.
Then, go back to PB and get the IMG address for the next picture...........
When you've got all of your pictures into your post then poke the button to get it to show in your MLF topic.