Go to Revise my Listing.
Go down the page to Picture.
Remove the current picture.
Add the picture again and check that the orientation is correct.
If it is not there is a round arrowy thing (note high level jargon usage there, eh?) Click on it until the orientation is correct.
Click to post the picture.
Scroll down to the bottom of the page,click for the next page.
Check that the picture is correct just before you click to list.