You almost got it. Hit your edit button and look at the address I used. The only difference is I opened the picture to the full size not the thumbnail. See in your address it says thumbnail and in mine it says medium? So open the picture to its big size before you copy the address.
So, am I to understand that doing them this way actually downsizes them so they are 256kb or less and will post? Been looking for a way to compress my pics. I've had to just keep cropping them til they were small enough. lol