You can set your tablet to use your fingerprint as lock code or to authorise iTunes and App Store purchases. To use Touch ID, you need to turn on the lock code.
Press Touch ID & Passcode.
Press Add a Fingerprint... and follow the instructions on the screen to add your fingerprint.
Press Continue. If you haven't previously selected a lock code, key in a code of your own choice twice.
Press the indicators next to the required settings to turn them on or off.
Slide your finger upwards starting from the bottom of the screen to return to the home screen.