https://www.gamespot.com/articles/fortnite-how-to-earn-a-free-battle-pass-tier-with-/1100-6458807/

Week 2 of Fortnite's Season 4 challenges have been released for Battle Pass owners. These offer a set of objectives to complete when you're not getting killed trying to become Thanos, and they each come with Battle Stars to level up and earn skins and rewards. But as with the first week, Season 4's new Blockbuster challenges offer a free Battle Pass tier--provided you've got a good eye.