In order to redeem Playstation Network Code please follow instruction below:
Go to http://www.SonyEntertainmentNetwork.com
Click "Manage Account" and sign in with your Sign-In ID(E-mail Address) and Password.
Click on "Redeem Prepaid Card".
Enter the code printed on the voucher or PlayStation Network Card and click "Continue".
If the code is valid, you will be presented with a description of what the code will deliver to your account.
Press "Redeem..." button to add the item or funds to your account.