At the bottom of the screen you should see a toolbar with app icons on it.
Swipe across to the end and look for the Sticker Drop app icon.
If you can’t see it, you might need to tap the More (3 dots) icon then tap Sticker Drop from the list.
Once selected you will see your Sticker Packs available for use. All you need to do is find the sticker you want to use by tapping the Sticker Pack icons
Tap and drag the Sticker into your conversation.
If you don’t like the size of the stickers you can drag the grab bar up to make Sticker Drop full screen and change the Sticker size to suit your needs.
If you want to add more stickers, tap the add (plus) button to be taken back to the main Sticker Drop app to add create some more stickers.