You have to add constraints programmatically if you want to achieve scrolling. And each side of your scroll view has to have at lest one constraint tied to it. So for example if you have 2 images you would have 3 horizontal constraints: |-firstImage-secondImage-| and 2 vertical constraints for every image: V:|-fistImage-| and V:|-secondImage-|. This way you can set the content size of your scroll view. You can find the Apple's guide here.
