Using reactions in a livestream is a great way to interact with creators and other users who are watching the livestream with you. Remember that not all livestreams will have reactions enabled, and reactions that are available will differ between creators. Available reactions and their individual cost is at the discretion of the creator.
While in the livestream, tap the reactions button on the top-right button panel.
Select a reaction that you want to send to the creator.
You will see the reaction in the livestream along with a verification in the live chat.