Normally something like the Deadpool skin would just be available to purchase with in-game currency, earned from playing the game, but instead Deadpool looks to be unlocked by executing secret challenges, and those challenges will be available over the course of the new season, so to get Deadpool, you’ll need to keep coming back to Fortnite over the next few weeks.
While Deadpool joining Fortnite has certainly succeeded in increasing interest in the game, those players will have to wait and see exactly what is needed to unlock the character.