How do I react to a message?

To react with ❤️, double-tap a message. For other emoji, press and hold the message and pick from ❤️ 😂 🔥 😍 🙌 👀 ✂️ ✨. A message can only have one reaction, so picking a different emoji replaces it. Tap the same emoji again to remove it. The other person sees reactions right away.