Enabling fingerprint lock in WhatsApp is a simple process. Follow these steps:

1. Open WhatsApp: Launch the WhatsApp app on your smartphone.
2. Go to Settings: Tap on the three dots in the upper right corner to open the menu, then select "Settings."
3. Account: In the Settings menu, tap on "Account."
4. Privacy: Next, select "Privacy."
5. Fingerprint lock: Scroll down and tap on "Fingerprint lock."
6. Enable Unlock with fingerprint: Toggle the switch to turn on "Unlock with fingerprint."
7. Confirm Fingerprint: Follow the on-screen instructions to confirm your fingerprint. You might need to scan your fingerprint to confirm.
8. Set Auto-lock Time: Choose the amount of time before WhatsApp locks automatically, which can be immediately, after 1 minute, or after 30 minutes.

Once you've completed these steps, WhatsApp will require your fingerprint to open the app, adding an extra layer of security to your chats.