When you go to the "Start a New Thread" button if you scroll down to where it says "Manage Attachments" If you click on that you should get another pop up window with 2 spots use the one says "Browse"--this will take you looking thru your computer once you find your photo click on the "Upload"button its blue. It will work for a bit then it will show up in green words a few lines below where you uploaded it, you can then just close that window and post and everything should be in your post.
Hope this helps more than it confuses
Merry Christmas