why can't I post pics?

I'm new here and want to post pictures of 3 steers that I'm trying to pick from but the post won't show up.  When I tried to do it for the second time it said I had already posted this but it never showed up.  What am I doing wrong?

Make sure that you click on additional options. I would go ahead & reduce them to about 800 x 700 size. It will take a minute for them to load.If you're trying to post an unaccepted type of pic it will let you know. The only time I've had that message was if I got logged out because of time, then logged back in & tried to back up & repost it. It wouldn't do it, you have to retype everything.