When you find a Lucky Card that you have already found before (a duplicate card), you will collect the Extra Stars from this card into your Extra Stars meter. Fill the meter to win a Scratcher! Rarer cards have more stars and will fill the meter faster. Scratchers can be found in the Scratcher Lobby.
Fill the Extra Stars meter with stars from your duplicate cards.
Find your Scratcher rewards in the Scratcher Lobby.
Note: You can turn off Lucky Card Pack notifications in the game Settings menu. You will still be informed when you win Scratchers or Credits!