How to Set Up Fingerprint Security in Galaxy S9|S9+?

Register a Fingerprint: First you’ll need to register your fingerprint. Open Settings, and then search for and Select Fingerprint Scanner. Follow the on-screen prompts to register your fingerprint. If you haven’t set up a Pattern, PIN, or Password yet, you’ll be required to. Make sure you remember it, as you’ll need to unlock your phone after it restarts or when it hasn’t been used for more than 24 hours. 

Add Additional Fingerprints: If you’re ambidextrous, you might want to register two fingerprints so that you can unlock your phone whether it’s on your left or right hand.
To add a fingerprint, Open Settings, and then search for and select Fingerprint Scanner. Enter your credentials, and then touch Add fingerprint.

Fingerprint Verification for Apps: You can use your fingerprint to verify your identity on supported apps and make payments quickly and securely with Samsung Pay. It’s all at your fingertips! To see these options, Open Settings, and then search for and select Fingerprint Scanner. 

Enter your credentials, and then look under FINGERPRINT VERIFICATION for the following options:

• Samsung Pass: Use your fingerprints to verify your identity with Internet and other supported apps. 
• Samsung Pay: Use your fingerprints to make payments quickly and securely.