To complete one of the Week 1 A New World challenges, you'll need to use one of the game's new weapons: the fishing rod. Unable to hurt opponents, you will therefore have to go to the edge of a lake or a river, and thus fish to find a weapon in it. Completing this challenge will therefore require you to relax and enjoy.
For this challenge, you will need to go near a water point equipped with a fishing rod. Lay down quietly, and cast the line to start fishing. The rest will happen naturally. Go up the line as soon as it dives, and repeat the operation until you get the weapon that will make you complete the challenge.
As a reminder, it's easier to complete this challenge in Team Rumble, then with respawning, you won't have to worry about dying.