For online multiplayer modes 'Casual' and 'Ranked', each player will need their own mobile device (Android, iOS) with the RISK application installed. In a private 'Casual' game with friends you have 3 ways to join: 

  1. Enter your friend's Game ID.
  2. If you're RISK friends with the host, they can send you a game invite.
  3. If you're over 13 years of age, have opted in to detecting local WiFi games, and are connected to the same local WiFi network, the RISK app should automatically detect and list your friend's game.