You nearly had it. Once uploaded, you just click on the picture and a list of options appear. change “use thumbnail” to “use original” and send to editor.
I’ve taken the liberty of adding those pictures to your post.

Earlier today, I tried out my new kitesurf kit and not only did I manage to lacerate my feet on what seemed to be sharp coral, but I also lacerated the kite. I shall be avoiding East Beach, Littlehampton at low tide from now on.