6. What he said...basically you can't post a photo/pic... you post the LINK to
said photo/pic, which must be online somewhere. If you have a photo on your computer you want to share, you have to go to a site like photobucket and upload it, then copy the link of that photo and paste it here in a post on DU.
Try it a couple of times and do preview and you'll get the hang of it.