Apple iPhone 5s (iOS8)

Press Settings.

Press Touch ID & Passcode.

Press Add a Fingerprint....

Follow the instructions on the display to add a fingerprint.

Press Continue.

Key in a phone lock code of your own choice.

Key in the same phone lock code again.

To use Touch ID as phone lock code:

Press the indicator next to "iPhone Unlock" until the function is turned on.

To use Touch ID to authorise iTunes and App Store purchases:

Press the indicator next to "iTunes & App Store" until the function is turned on.

Press Settings.

Press the Home key to return to the home screen.

Touch the Home key to scan your fingerprint.