i created a slideshow but all the photos are now mixed up. i just dragged the event to a new slideshow. how can i get them into the same order they were imported in?

my slides are all mixed up after i imported them into a new slideshow. i just copied them from the events and dragged the icon to the new slideshow but the have re arranged themselves into a random order. I want them to play in the order i took them and copied them . How can i do this please. am working with iOS 7 on my iMac using iPhoto latest version.