How to update/insert an other document in cloud firestore on receiving a create event for a collection using functions

I have done it using below code

exports.userCreated = functions.firestore.document('users/{userId}')
.onCreate((event) => {
    const firestore = admin.firestore()
    return firestore.collection('usersList').doc('yourDocID').update({
        name:'username',
      }).then(() => {
        // Document updated successfully.
        console.log("Doc updated successfully");
      });
})