On this page of the Assassin's Creed Valhalla guide, you will find a detailed walkthrough of the Snotinghamscire side quest: The Good Man of Sherwood.
Reward for completing the mission: 1200 XP.
In the place indicated in the above picture, you will meet a group of people undergoing archery training. If you want, you can talk to Royc, whom you may have already met in the side mission A Cordial Invitation.
Stand next to the people who practice and shoot at the very center of the target to attract the trainer's attention. Talk to the woman in the helmet, and she will assign you the task of breaking two jugs in 20 seconds.
Once you have completed the previous task, talk to Little John. The man will task you with hitting the chicken hanging from the wooden pole at the top of the hill. Aim slightly above the target so that the arrow reaches the target. After passing this challenge, the mission will end.