Once you have unlocked your content, for example by redeeming a code on your platform, you should be able to find the new content in-game.
Depending on the content you unlocked, these are the items that will be added to your game:
Wrath M249
Legacy offroader
Hurkling outfits
Legacy offroader
Hurkling outfits
SVD Claymore
Sidecar motorbike
Sidecar motorbike
M113M shotgun
RAT4 rocket launcher
RAT4 rocket launcher
Deluxe Pack