X 2 welcome to BYC.Hello and welcome to BYCI'm not familiar with rooster booster, unfortunately, but I've dug up some older threads on the topic that says you add it to their water. Here's the ratio:
https://www.backyardchickens.com/t/732303/help-using-rooster-booster
https://www.backyardchickens.com/t/746126/rooster-booster-measurements
