Quote:WhatsApp has finally rolled out fingerprint lock support in the official app for Android after the company previously released similar capabilities on iPhones earlier this year.
 
Basically, the fingerprint protection means nobody but you can launch WhatsApp, so all your conversations are locked until you authenticate.
Furthermore, on Android the WhatsApp widget is also locked, so the latest messages that you receive are no longer displayed here either unless you allow the app to show content in notifications.

The new option is available under:
Settings > Account > Privacy > Fingerprint lock
 
Once enabling the Unlock with fingerprint option, you should see additional options that let you configure the behavior of this security system on your Android device.