If you pre-ordered Deus Ex: Mankind Divided there’s a host of awesome DLC content that you can unlock and use on your travels. This How To Access DLC Content In Deus Ex: Mankind Divided provides a simple guide on where you can find your DLC items and how you can activate them for use in the regular game.
When you begin the game there’s actually a tutorial on how to collect the DLC items in the menu but I’d totally missed that before spending a few minutes trying to figure it out. If you pre-ordered and got some costume options as DLC these are the easiest to access. Simply pause the game and go to the Outfits menu. From there you can change both the Tactical and Civilian attire that Adam Jensen can wear.
To access other DLC items such as weapons, you need to open your inventory. Scroll through with the shoulder buttons and make sure you’re on the first option, marked by a gun. In the lower left you’ll see a small tab labeled storage with the appropriate button marked. On the PlayStation 4 it is L2.
Simply hit the button and this opens your storage but be careful, you cannot transfer items back so try not to fill your inventory with all the weapons straight away.