NumantianGames.com

Just seems as if I must be missing something.
Not certain how to claim DLC on steam.
When I click on the link, where I am sent is the page on Steam that asks if I want to buy the DLC. And when I access the game otherwise, I am told I do not have any DLC.
I imagine there is a process that one can but in the code but not under the tabs located on the game (unless you use the same tab as the Beta?).

You should have received a code via mail.

You can then go to steam and click on +add a game on the bottom left.
Then Select "activate a product on steam"
copy/paste the code and that's it.

Thank you. Got it. Steam's explanation older than their update so did not quite match. Yours did.

Also a thank you from me. I couldn´t figure out how to activate it in Steam

I have a similar problem: I received the boxed edition of the game and can play it.
However a while ago I received two emails with Steam codes for DLC but Steam does not allow me to activate the DLC without activating the game itself first.
And I haven´t received a steam code for the game - should I have when I have the boxed edition with the physical box?

Edit: Problem has been solved by a message from Anubis.