anyone know where exactly can u redeem the key for the bonus content that came with limited edition i got the digital download from gamestop but it does not say where i can redeem my stuff any help would be appreciated ....for the PC version

in case you haven't been helped or got it, go to gamesas.com/limitededition

I've put my key in and it said it's a success but past that nothing else is happening so i'm stuck myself.