Listings may be edited completely as long there are no bids, and there is more than 12 hours left in the auction. If there are bids, or less than 12 hours left, you may only add to the description of the item.
To edit a listing:
Method 1: While you are logged in, navigate to the auction you would like to
edit, there should be an Edit Link in the upper left hand corner of the
auction title.
Method 2: 1) Navigate to the MEMBERS AREA > Selling / Sold > Open Auctions
2) To the right of each open item in the resulting list, there is a
link named "Edit Auction". Clicking the edit link will bring the item
into an edit screen where you may correct any errors or add/remove
pictures.