To turn the feature on in the app, go to Settings > Account > Privacy > Fingerprint lock and turn it on. You can set the app to lock immediately, or after one or 30 minutes.
Some Android phones offer app lock features within the OS that let you keep certain apps locked behind a fingerprint, but it’s good to see individual apps like WhatsApp offer it too. As WhatsApp is owned by Facebook, this could be a feature that extends to its other apps like Facebook, Messenger and Instagram.
Facebook owns too many big companies, doesn’t it?