Question: how to backup your whatsapp chats on icloud?
Answer: Open Settings, tap on the Apple ID banner at the top, and then tap on iCloud.
Scroll down to find WhatsApp in the list and tap the switch to toggle it on.
Launch WhatsApp.
Tap on the Settings menu (the gear), then the Chats button, and Chat Backup.
Tap Back Up Now to run a backup.