This challenge is part of Fortnite Chapter 2 Season 1 "Alter Ego" Mission. You'll have to heal a teammate with a Bandage Bazooka while wearing the Remedy outfit. This weapon was dropped into the game at the beginning of Chapter 2. It's of epic rarity and, hopefully, you'll find one in chests or supply drops.
This challenge is extremely easy to achieve if you are a little prepared. First of all, treating a teammate already requires having one! You'll have to play in Team Rumble in duo or squad to be helped by other players.
Note that the Bandage Bazooka can be used on yourself but the challenge requires you to heal a teammate, not you.
To complete this challenge, you'll also need to wear the Remedy outfit. It's a skin that you get at Level 40 of the Battle Pass. This challenge is only available if you have previously completed a total of 5 missions.
