Phil, you can add a pic to your post if you click on the "+ Additional Options" below the text entry box, then click on 'choose file' near the 'attach' text. You are limited to a small file size, so you need to size the picture down to 640px or so.
There is a better but more complicated way to do it by uploading to a photo hosting site, then inserting the link too. On my 'to-do' list is create a step-by-step how-to document for that.