Samsung Galaxy S10 and S10+ don't come with a physical fingerprint sensor, not on the back not even on the side, the fingerprint scanner is actually inside the phone’s screen, near where the Home key is located.
Note: You need to have a lock screen set up to add your fingerprint.
Please follow the steps below to setup Ultrasonic Fingerprint
Go to “Settings”.
Tap “Biometrics and security”.
Enter your PIN, pattern or password. If you haven’t set one, you will be asked to register one first.
Place your finger on the sensor area (as indicated on the screen) and keep pressing it until your fingerprint is fully captured. The fingerprint image will be completely blue when the process is complete.
Then, to get a full scan, rotate your finger on the sensor to capture the edges of your fingerprint.
Once complete, tap “Done”.
It will then show as “Fingerprint 1” on the display.
How to use it
To unlock your phone, tap the screen or press the Power button.
Then, place your finger you used during setup on the fingerprint icon. The phone will automatically unlock if it recognizes your fingerprint.
How to remove it
From Settings, search for and select Fingerprints.
Touch Fingerprints and enter your security credentials.
Touch the fingerprint you want to delete (i.e. Fingerprint 1), and then touch Remove. Next, touch Remove again to confirm.