You can find the Castor Woods Prepper Bundle items in your in-game stash. The in-game stash will become available to you during the second quest, ‘Safe Haven’.
To access your Deluxe Edition Digital Content:
Visit dyinglightgame.com/deluxe-edition, create a Dying Light Outpost account (if you don’t have one already) and connect your platform of choice. Please note: this is the same account as on Pilgrim Outpost.
Once linked, click the ‘Download’ button and you’ll get your Tourist Map, Wallpapers and Official Soundtrack.
Note: Before doing this, you must have played Dying Light: The Beast at least once while being online.
[Steam only] If you own the game on Steam, you can also find your Deluxe Edition Digital Content in the game’s installation folder:
Open Steam → right-click the game → Properties → Installed Files → Browse Local Files
Inside the installation folder, open the “Deluxe Edition Digital Content” folder to access your items.