Open WhatsApp on your iPhone
Tap Settings
Tap Chats
Tap Chat Backup
Tap Back Up Now
To enable automatic backups, tap Auto Backup
Choose backup frequency
Make sure iCloud Drive is turned on
Make sure you are signed in to iCloud with the same Apple ID
Ensure WhatsApp is allowed to use iCloud
Connect to Wi-Fi if needed
Keep your iPhone charged during the backup
Wait for the backup to complete