After you choose attach a window will open up. Then you choose the file with the choose file selection. Then it will open a window to your pc pictures. Choose a pic. Then in the same widow choose upload. Then close the window. Then you will be back at your post here's what I think your missing. Scroll all the way down to the bottom of the page and hit the submit on the second window not the submit on the first one. If that makes sense lol. If you chose submit on the first window I don't think it will post the pic however if you choose submit on the second window it will upload the pic.