Because I also wondered about this when I first became a member, and find it easier to
see how to do something then read about it - I have attached a PDF document that contains a series of screen shots that show exactly how to upload photos. I collected these screen shots as I replied to your message.
Images can be uploaded in full size, or as thumbnails.
Full-size images make it more work to scroll through a thread (I learned the hard way!).
Thumbnail images expand in a separate window when people click on them so that seems to be the way to go.
As an example, I'm attaching
full-size image of my wonderful dog when she was a puppy, and a
thumbnail image of me standing on top of St. Regis mountain in winter.
Fun fact: St. Regis mountain is located close to Paul Smith's College, the site for this year's Annual Assembly, and has a wonderful hike to the fire tower on top!
There is a FAQ about loading images here:
http://www.wcha.org/forums/index.php?threads/how-to-post-photos.469/