When you sign in with a password for the first time, Jabber will ask whether you'd like to use fingerprint or face recognition. Tap Yes to make this your default sign-in option.

The next time you start Jabber, follow your device's instructions to sign in with fingerprint or face recognition. If it doesn't work after three tries, you'll be asked to enter your password.

You can stop Jabber from using fingerprint or face recognition. Tap your profile picture, and then go to Settings > Privacy.