On this page of Assassin's Creed Valhalla guide you will find a detailed walkthrough for Winchell the Robesfree.
Rewards: 1,200 XP.
In the place marked in the picture above you will meet a man named Winchell, who is standing on a rock shouting insults - naked. Winchell founded a nudist club and now he has been banished from it so he wants revenge on the people that did it. Your task will be to go down to a nearby nudist camp and steal the things of the people who are there.
When you find yourself in the camp, one of the women will inform you that everyone has put their belongings in a nearby box, and when you talk to her, she will ask if you want to join them.
As soon as you pick up the box, the nudists will immediately realize that you're stealing their stuff and they'll chase you. You don't have to fight them, all you have to do is take the box to Winchell, put it by his tent and talk to the man to finish this task.