If you are having a Google play gift card code or promo code in your hand and want to use it to shop some games or applications on the Google play store using your Google play gift card or promo code that you have. You can redeem your Google play gift card or promo code by signing in to your Google account and visiting the web http://play.google.com/redeem in order to redeem the card so you can use it to buy some application goods on the Google play store that is provided by Google.
Another way that you can do in order to redeem your Google play gift card or promo code is by installing the Google play 3.8.15. You need to download the Google play 3.8.25 to your device first before you decide to install the application on your android device as a regular app. After you are finally done with the installment process of the Google play 3.8.15, then you need to visit the http://play.google.com/redeem link and open it up in the play store and not from your browser. Another easy way to do it you can email yourself the link of http://play.google.com/redeem then select play store while opening the link.
After you are done with that, you will be taken to the redeem page on to the Google play store. Once you see the redeem page then you need to put and enter your Google play gift card code or promo code, next you need to press redeem after you enter the code. And once the redeem process succeed, you will have some amount of money depend on the value of your Google play gift card. You can use the money to spend on the Google play store to buy some applications in there for grabbing some digital goodies to your device. Good Luck !