To post a photo right from the iPhone get the App TapaTalk. It makes it easy. It does post the photo to their server so in a couple of years on Pelican it will be just a little red x when it is deleted.
To post photos from computer is a lot easier. Just hit the big yellow Go Advanced button, than click the big blue "Click Here to Upload Photos" abd you can drag and drop up to 10 photos per post maximum.