Do you mean to open the lock screen? If you set up fingerprint unlocking, you will have to set up a backup PIN or password for security reasons. It sounds as if you have not chosen to use the fingerprint method, but are using a PIN, unless I have failed to understand what you are asking.
To change from one method of unlocking to another, you may have to Clear Credentials in Settings, Security, and then set up the new method.
Posted via the Android Central App