With iMessage apps, the apps are literally inside iMessage.
- Launch Messages from your Home screen.
- Tap on the Apps button. (Looks like the App Store icon.) If you’ve already begun typing, it will be hidden and you’ll need to tap on the Show More button to the left to reveal it. ( > )
- Swipe to switch between different sticker packs.
- Tap on a sticker or touch and drag to peel it off and place it in your messages.