With your account and the launcher, you'll have access to all of the games available from Epic Games.
To download Fortnite, you'll need to create an account and download the Epic Games launcher. Fortnite has three game modes: the paid-for Save the World where teams of up to four players fight off zombie-like creatures and complete various missions Battle Royale, a free-to-play battle royale game in which up to 100 players fight to be the last person standing and Creative, a free sandbox experience where players can create their own worlds, platformer challenges, and battle arenas.
