How to get DLC?

[Druid of Lûhn]

I got Lord of the Rings: War in the North, special edition (DVD) and got downloadable content.
It tells me to go to the Xbox live website, but there it wants 25 digits (I have 15).
I was told on their forums to ask here.
So is there anywhere that we can redeem codes for games?

[DeGroot Keeper]

in steam click on games and then activate a product on steam.

[Druid of Lûhn]

And that gets me DLC?

[Tzafad]

Yes, you have to put in the Product Key when asked.