HELP in using Iphoto 11

Several things have changed in Iphoto 11. How do you flag a photo now? How you do tell iphoto NOT to display already imported photos from you ipad, iphone etc., how do you make a photo your desktop now? I also have a few problems using Icloud---example: took about 30 photos on iphone, came home, all are on wifi, only THREE of the photos appeared in the photo stream, so still had to plug in and sync...annoying. I also had quite the time figuring out the facebook connection, but found that! Please advise!

Thanks!