I get the hazop forest armor on code or in an email what is that all about
Did you pre-order the game? Because if so, that’s a long time to wait…
If your not using it, can I have it? Lol 
A bit late to be mentioning this.
It would have been printed on your receipt when you picked up the game from GameStop. If it’s not there, you would need to go back to GameStop with your original receipt and ask them. If you ordered online, you would need to talk to the online support and have your original email receipt.
Did you pre-order the game from Gamestop? If so, do what Vektor0 said. If not, however, then you’re almost out of luck. You can’t pre-order Halo 4 anymore, but if you still want it, then buy the Game of the Year edition, it comes with Hazop FOREST and tons of other bonus content!