Open Messages or another app that supports stickers
Tap the text field
Tap the sticker icon or the Apps button
Select a sticker pack or built-in stickers
Tap a sticker to send it
Touch and hold a sticker to drag it into a message
Tap a sticker to add it to a photo or message if supported
Use the App Store in Messages to download more sticker packs
Manage sticker packs in the Messages app settings if needed