Open the Messages app
Open a conversation
Tap the App Store icon next to the text field
Tap the stickers icon
Press and hold the sticker you want to edit
Tap Edit Sticker if available
Use the editing tools to adjust the sticker
Tap Done to save changes
To remove a sticker, press and hold it, then tap Delete
To reorder sticker packs, go to the sticker drawer and drag them into place
To create or edit a custom sticker, open Photos or a supported app and use the sticker options there