Sorry, but this may be US owners only. But give it a try and see: 1. Download the app Gift Voucher from the app store. Its a Nokia/Microsoft official app 2. Ensure you have your Wallet set up. Wallet is a built in app on your phone, but you need to sign into it first, if you have never done it. 3. Open the Gift Voucher app. Copy your code when it shows at the top. No code = you are out of luck 4. Go to wallet app and hit the + sign at the bottom 5. Click the Redeem Microsoft Credit 6. Paste in your code 7. Enjoy your $25 in app store credit. Now when you click on to buy an app, ensure that you pay with your Microsoft store credit Pics showing the steps below.