From VG247: “Youll need to bring your best moves to the dancefloor if you want to complete this Battle Pass challenge in Fortnite.
In order to complete this challenge, youll need to head over to the abandoned mansion near Lonely Lodge and cut some mad shapes on the dancefloor against an opponent or with a teammate. Theres a dancefloor and scoreboard in the basement of the mansion so you can keep tabs on who has the best moves.”
Source: N4G PC Fortnite: Compete in a Dance Off at an abandoned mansion