There are 2 ways to restore you purchases. The easiest way is to tap the Store button within the SNOOP app. Then, tap the Restore button on the bottom right in the blue bar. Login to your iTunes account to complete the process.
Another way is to tap on a puzzle pack that you have previously purchased. A dialog box will open asking if you want to purchase the pack. Select Yes. The app will then check to see if you have purchased the pack previously, if so it will prompt you to restore the purchase. You will not be charged for the purchase twice!