When logging in to the app for the first time, you will see a message that says ‘Login with Face ID/Touch ID next time?' If this is enabled on your device, this box is automatically ticked. Untick this box if you do not wish to log in with Face ID/Touch ID in future.
Once you have logged in with your username and password you will be prompted to place your finger on the fingerprint scanner to confirm your fingerprint or your face will be scanned by your device. The next time you log in you can use that fingerprint or face instead.