Good, makotto is right. You need to create your cards, split them and then shuffle you array:
(the +1 is your card back)
Event 1: On start of Layout=> Set DeckArray width to NumberOfCardsInYourDeck +1
(I am assuming that frame0 is your card back and 1 to whatever are your card faces)
Event 2: For 0 to NumberOfCardsInYourDeck ("deck") => Create Card at X,Y (it doesn't matter yet), set Card.ArrayNumber to loopindex("deck"), DeckArray set value at loopindex("deck")
Event 3: Compare 0 < Card.ArrayNumber >= NumberOfCardsInYourDeck/2 => set position to X, Y (pile 1)
Event 4: Compare NumberOfCardsInYourDeck/2 < Card.ArrayNumber >= NumberOfCardsInYourDeck => set position to X, Y (pile 2)
(Now you shuffle like in the tutorial)
Event 5: For 1 to NumberOfShuffles => set Slot1 to ceil(random(0, NumberOfCardsInYourDeck)), set Slot2 to ceil(random(0, NumberOfCardsInYourDeck)), set Card1 to DeckArray.At(Slot1), set Card2 to DeckArray.At(Slot2), DeckArray set value at Slot2 to Card1, DeckArray set value at Slot1 to Card2
For each Card => set Card.FaceFrameNumber to DeckArray.At(Card.ArrayNumber)
When you flip cards: set animation frame to Card.FaceFrameNumber
Cards created, split and shuffled!
Hope this helps.