Okay so I stumbled around for like a half hour before I figured it out, and it wasn't super obvious. Incase anyone else stumbles on this thread and finds no answers...

You need to get your product code for the game, and put it into steam to unlock it.

-Click your Account name in the top right of the Page.
-Click MY PROFILE
-Click HISTORY
-You will see your purchase. Next to COMPLETED TOTAL, click the three vertical dots.
-Click SHOW GAMEKEY(S)
-Enter your password.
-Copy your FULL GAME (STEAM KEY):
-Open Steam
-In the bottom left corner, click + ADD A GAME...
-Click ACTIVATE A PRODUCT ON STEAM
-Click Next
-Click I Agree
-Enter the product code.
-Hit next.
-Your game will now show up in your Steam Games Library under WARHAMMER 40,000: INQUISITOR - MATYR
-You can now download/install the game as you would any other steam game.

Awwwww y.y

Evrytime i try to click on History i get this statement:

"Whoops, looks like something went wrong."

Can someone help pls?

ty very much!