You get the bonuses immediately/instantly at the start of the game. All you have to do is wait for the doctor to give you the Pip-Boy to access it.
You can also receive the packs for each new game or new character that you start. So you can start a new playthrough as many times as you want and still get them. I have tested this to confirm it.
So I hope this puts some minds at ease.
My bad if this topic has already been created, I didn't see it when searching.
Also: All pre-order bonuses come inside of the game box on the "Added Bonus" paper which is underneath the advertisemant paper for Brink and Hunted: Demon's Forge. (The added bonus is on its own piece of paper.)
Can't get more specific than this. I hope this helps.