To add a player to your Friends list, you need to send them a Friend Request, which the player will have the option of accepting or declining.

After you have sent a Friend Request to the user, the user will appear in your Friends list with an icon next to their name indicating that you've sent them a pending request.

If they accept your request, the sent request icon next to their name will disappear, indicating that they have accepted and are now one of your Friends. If they decline your request, their name will disappear entirely from the list.

To invite players to join your Friends List, you can use the Xbox Dashboard, or you can invite them through the interface of the game during a game session.

You can always remove a player from the Friends List from the game interface, or from the Xbox Dashboard. When you remove a player from your Friends List, you are removed from their list as well. If a player on your Friends List does not appear, they may have left the service and are no longer an active player.