I think i know what you did. You used the paperclip icon and tried to attach them, right?
For images, you can use the attachement emblem, but you still need to get the URL that it will give you to post for your picture, or you need to upload them to a site such as
imageshack or
photobucket. I personally use photobucket. I believe you can upload to imageshack without creating an account, but you are limited. I know photobucket accounts are completely free, and i believe imageshack is the same.
Once the images are uploaded to a site that can host them, you put image tags around the URL given to you by these sites. The image tags are [IMG]yourURL[/IMG]. Or you can click on the yellow image of the mountain, and insert the URL in the box that pops up here on the forum, and hit okay and it will add the IMG tags for you. Then when you hit post, you image will appear.