https://www.gamespot.com/articles/fortnite-challenge-guide-season-5-where-basketball/1100-6460526/

Season 5 of Fortnite: Battle Royale rolls on, and the latest batch of challenges is now available to complete for Battle Pass owners on PS4, Xbox One, Nintendo Switch, PC, and iOS. As usual, Week 2's challenges consist of seven different objectives, which run the gamut from eliminating a certain number of players to searching a specific area of the island. One of the potentially trickier tasks is to score a basket on five different hoops; here's where to find the basketball courts with those baskets and how to complete the challenge.

To complete this challenge, you will first need to have unlocked the basketball--one of the new toy items introduced in Season 5. The basketball is earned upon reaching tier 11 of the Season 5 Battle Pass. Fortunately, this can be accomplished fairly quickly, so if you own the Battle Pass and have been playing regularly, there's a good chance you already have the basketball. Once unlocked, you use the toy in the same way you would use an emote by assigning it to an emote slot before a match and pressing the corresponding key or button.