iMessage requires you to create an app with Xcode that loads the sticker to iMessage. sticker-convert automates the creation of the Xcode project.
- In sticker-convert, select compression preset and output option to imessage.
- Open the Xcode project created by sticker-convert.
- You may test the sticker pack with the play button on the upper left corner. This will build and launch the sticker app in emulator for you to test.
- You may sideload the sticker app to your apple device (Not tested).
- You may pay a fee to Apple and publish the sticker app for everyone to use.