iOS
To restrict in-app purchases on your iOS device, please follow the following steps:
Click the 'Settings' icon → Click 'General' → Click 'Restrictions' and then select 'Enable Restrictions' → You will be asked to enter your passcode → Re-enter the Passcode.
Then, look for the 'In-App Purchases' option and turn it off by scrolling to the left.
Android
To restrict in-app purchases on your Android device, please follow the following steps:
Enter the Google Play Store app → Click the 'Menu' button → Select 'Settings' option → Look for the 'User Controls' section and select the 'Require password for purchases' → Select the first option 'For all purchases through Google Play on this device'.
You will now be asked to enter your Google Play password for all purchases.
Please note: the instructions above may vary on different devices.