Youll have to redeem it online through the playstation website from a computer. You wont be able to redeem it from the ps3 system.
Heres the steps on doing so:
1. Go to http://account.sonyentertainmentnetwork.com.
2. Login to your PSN account.
3. Select 'Redeem Prepaid Card'
4. Enter code and click 'Continue
Hopefully it goes without saying but you wont be able to play the game until you get your ps neo and download it from your account .Redeeming it this way will at least place it in your game library on ps4 though so that once you get it all you would have to do is download it.
Heres the steps on doing so:
1. Go to http://account.sonyentertainmentnetwork.com.
2. Login to your PSN account.
3. Select 'Redeem Prepaid Card'
4. Enter code and click 'Continue
Hopefully it goes without saying but you wont be able to play the game until you get your ps neo and download it from your account .Redeeming it this way will at least place it in your game library on ps4 though so that once you get it all you would have to do is download it.