Using Photobucket or a similar site:
1: You need to first post the pic on an image hosting site like www.photobucket.com. Make sure the album is set for public viewing and not private.
2: Once you save the pic there, you will have three options
Highlight the IMG link, right click and select copy. Then right click and paste it into your post.
It will should look like this
(I'm not taking credit for this.. it was done by BigCT.. just thought I'd move it so it could be found easily!!)