Currently WhatsApp only supports this additional security feature on Apple devices. To use the feature you'll need to ensure you're using the latest version of WhatsApp. If you don't have the latest version, head to the iOS App Store and hit the update button. To enable the new authentication feature you'll need to open WhatsApp and head to the settings page. That alone will be enough to persuade some people to enable this feature, I'd imagine.

Source: Forbes February 10, 2019 20:15 UTC