If you haven’t chosen a 4-digit restrictions Passcode before, you’ll have to do so now by typing it twice before continuing. Record your Passcode somewhere safe. You’ll need the Passcode to enable In-App Purchases in the future.
Tap ‘Enable Restrictions’.
Scroll down until you find 'In-App Purchases' and tap the green switch to turn off In-App Purchases.
Start the Google Play Store app from the Home Screen.
Tap on the ‘Menu’ button and tap ‘Settings’.
Scroll down to the “User Controls’ submenu.
Tap on ‘Require password for purchases’.
Choose the frequency with which you want the device to require a password.
Choose a PIN that will be easy for you to remember, but hard for the kids to guess, and re-enter it after tapping 'OK'.
Open up the Amazon Appstore App.
Select 'Menu', then 'Settings', then 'Parental Controls'.
Choose 'Enable Parental Controls’ and enter your Amazon Password.
If you would prefer to use a new PIN select the ‘Use PIN’ box.