Bring Peace to Hyrule is part of the side adventures you can take in Zelda: Tears of the Kingdom to earn money and grow in combat potential.
These adventures are present all around the map of the game, and you will get to attempt them with your progression. You can take on this side adventure quite early in the game as it is found in the initial region of Tears of the Kingdom.
How to unlock Bring Peace to Hyrule in Zelda: TotK
Make your way to the Passeri Greenbelt area in Hyrule and reach the location marked on the map below. You will come across a group of warriors heading out to get rid of some monsters.
Speak with their leader and you can join their force. This will start the “Bring Peace to Hyrule” adventure in Tears of the Kingdom.

How to complete Bring Peace to Hyrule in Zelda: TotK
Your sole objective is going to be the complete elimination of all monsters. Make your way straight after conversing with the members, and you will find a large battleground with wooden walls.
You need to fight the monsters waiting inside but be careful. This “Bring Peace to Hyrule” side adventure is one of the earliest in Tears of the Kingdom, as mentioned, so your health bar is not going to be that great. You must keep some good food items to heal yourself during the battle.
During the combat, your allies will significantly help you take down the monsters, so the key is to stick together and dodge enemy attacks.
Once you are done with every beast, you will complete Bring Peace to Hyrule and will earn 100 silver rupees in Tears of the Kingdom.