You have to set up Screen lock first before you set up Fingerprint unlock.
1. Go to
Settings > 
Passwords & security > Fingerprint unlock.
2. Verify your identification with a screen unlock.
3. Add your fingerprint on the fingerprint scanner.
4. Tap Done.
Note
The place of fingerprint sensor may vary in different models. The fingerprint sensors may locate on the sides of the phone or in the bottom of the screen.
1. Go to
Settings > Passwords & security > Fingerprint unlock.2. Verify your identification with a screen unlock.
3. Add your fingerprint on the fingerprint scanner.
4. Tap Done.
Note
The place of fingerprint sensor may vary in different models. The fingerprint sensors may locate on the sides of the phone or in the bottom of the screen.
Tip
Make sure both your finger and the screen are clean.