There are two options to start a private game.
- Join an existing private game with a room code.
2. Send a game invittation to a player that is allready added as a friend within the app. This only works if you have friends added to your account. If the app is closed on the phones of invited players, they will receive a Push-Notification (if enabled).
You can combine both methods, eg. invite friends and also let people join the same room with a room code.