Activate any of the additional content (DLCs and the Expansion) or just play the base game.
XCOM 2: Aliens rule Earth, promising a brilliant future for mankind while secretly hiding a sinister agenda. As the leader of a guerrilla force facing impossible odds, you must ignite .The XCOM 2 Collection includes the award-winning strategy game XCOM 2, four DLC packs (Resistance Warrior Pack, Anarchy's Children, Alien Hunters, Shen's Last Gift) and the War of the Chosen expansion all in one package.