You have to add the Mouse&Keyboard object to your layout (assuming you haven't already).
Then in your event editor you set up your event with the Mouse&Keyboard object like so:
-> M&K On Left Clicked on cardSprite
+ do stuff
Here's a little test .cap to show you how you might do it:
http://www.mediafire.com/?blzyjuwnzfn
It's very basic, but it works. Click a card, then click a space, and the card moves to that space.
It works by putting the unique ID of whatever card you clicked into the global variable "cardPicked." Then when you click a space, it checks to see if there's a card picked (cardPicked > zero). If so, it looks up the family "Cards" and finds the one with the UID that matches cardPicked, and positions just that one. Then it resets cardPicked to zero.