Click reply, and type your message, and then scroll down the page a little and click the Manage Attachments button. (Make sure your pop up blocker is off) Then, make sure that your image is actually uploading. I've had trouble with everything but jpeg files, they have to be less than 2000 by 2000 pixels. Once you have found the file, click upload, and then wait till it says image uploaded. It's not a huge message, it's just one line that pops up, you have to watch for it. Once it shows up, kill the pop up that appeared when you hit manage attachments, and hit post. Good luck!
Early to bed early to rise makes a man stupid and blind in the eyes - Orson Scott Card