我在Xcode 6中使用多个UIImageView时遇到了麻烦

I put a uiimageview onto my storyboard, in my view controller folder, and when I go to put another image view on the story board, it automatically takes up the whole screen and blocks the other picture. I tried to add the second uiimageview to my view controller folder to set a hierarchy but it won't let me add it.I put a uiimageview onto my storyboard, in my v