You'll need to help Flo to catch as many of the malfunctioning robot elves as you can!  To find the elves, play the level they're hiding in, and catch them by tapping on them in the mini-game that will appear at the end of the level.  To help find the level that the elves are hiding in, tap on the "Find Now!" button in the bottom left.

As you collect elves, you'll earn exclusive prizes!  Event prizes include a holiday themed decor set--for Greasy Spoon, Deep Sea Diner, and Rocket Diner!--two exclusive hats than can only be won in the event, and a permanent energy cap increase!

When you've earned a reward, Flo will let you know!  Go back to the main event screen (Click on the button with the holiday wreath to bring it up) and claim your prize!