How do I turn on Face ID or fingerprint sign-in?

Open Profile and look for Face ID / Touch ID quick sign-in under Security, then switch it on. You'll be asked to confirm with your face or fingerprint once to set it up, and after that, opening the app just needs a quick scan instead of typing your phone number every time.

You can turn it off the same way, any time. And if you ever land on the quick sign-in screen and it's not you, tap "Not you?" to fall back to signing in with a phone number instead.