How to Use a Key for Custom Matchmaking? Once you've gotten your hands on a key, hit the Custom Matchmaking button in the bottom right corner once you're in the lobby.

Everyone wants to know how to make a custom game and how to get a matchmaking key - here's all you need to know.

You need a custom matchmaking key in order to set up your own game and it ensures that you can control who is able to join the game, instead getting random people added.