First copy the URL of the photo (the one ending in .jpg or .gif) into your post. Then highlight it, and click the little icon that looks like a picture (to the right of the one that looks like a globe, and under the S
That will embed the URL of your photo between two "IMG" tags and should display it within your post.
(to get the URL of your picture, open it up and right-click on it. Then go to "properties" and the URL should be listed there. Highlight and copy it )