look on the bottom of the page when youre setting up your ad........and click options. click upload file. click choose file and retrieve your pic and load it in the program. click full size. make sure the curser is at the bottom of your message or the pics will split your dialog. post it. make sure you do it right. you only have a few minutes before it times out and you cant edit. good luck.
if you cant edit it because it timed out, just post big pics on a new line entry. on any new ads, just click the larger option before 5-10 mins passes.