Easy Steve......you need a photobucket account.........then just upload from your computer downloads/photos, etc, that you want........
When you've brought up the image in photobucket that you want to post on the Forum, you need to look to the right and click on the box marked "HTLM"............this should then go "copied".........
You then need a link open (new message) on the Forum, and the best thing to do is to press "CTRL" and "V" button on your keyboard together and the copied link will appear as a jumble of text.........ignore this and post any text you want either above or below this............
Then simply do as you would do normally to post.......