Support
Getting stickers out of WhatsApp
Open the chat with the most stickers (a group chat is ideal). Tap the name at the top → Export Chat → Attach Media. In the share sheet tap Add to StickerHop. Only stickers that were sent in that chat are included; forward your favorites to your own chat first if they live only in your tray.
Where StickerHop is in Messages
In any chat tap the + button to the left of the text field, scroll down, and tap StickerHop. If it is missing, scroll to the end of the sticker row → Manage Sticker Apps → Edit and switch it on, then force-quit Messages once.
Saving a sticker into the iOS Stickers section
In the StickerHop panel switch to “Saveable image”, send the sticker, then long-press it in the chat and tap Add Sticker.
An import seems stuck
Large exports take a moment. You can leave the app; it resumes where it left off next time you open it and notifies you when done.