Nintendo game cards allow you to purchase additional games, applications, and unique content directly to your Nintendo console or handheld. These prepaid gift cards come in a number of different values.
1- On your Nintendo device, select the eShop icon at the Home menu.
2- Scrolling to the left will present the option to ‘Add Funds’.
3- Click the “Redeem a Nintendo eShop Card” button.
4- Simply input the code of the card which you have bought and select ‘OK’, to credit the funds to your Nintendo Network ID.
5- Now you’ve got your Nintendo account loaded, and ready to get any new game or application.