Mary Ann, first do a search to see if it already exists in the database, and then you can just add a photo (scroll down the page to beneath the entry). But if it doesn't already exist and you're adding it to the database, I just fill in with "Iris" until you hit the "cultivar" name -- that's the name of the iris. Then submit it, and then it has to be accepted by the Systems Administrator and you'll later get a Systems Message that it has been added, and then you can add your photos.
Also, if you hit "Watch" up in the left corner of a forum it will save it for you, and then anytime when you're in ATP all you have to do is click on the "All Things Plants" in the upper left corner and it will take you to your list of forums and there will be a red "Yes" by any that have new activity. And when you want to check a thread in a forum with a red "Yes" at the beginning, just click on the "Yes" and it will take you to the first unread message.
It's really very simple once you get the hang of it!