How to implement Touch ID in iOS app?
Tap Settings > Touch ID & Passcode, then enter your passcode. Tap Add a Fingerprint and hold your device as you normally would when touching the Touch ID sensor. Touch the Touch ID sensor with your finger—but don't press—so the device can begin recognizing your fingerprint.
How do I change my Touch ID password for apps?
On your iPhone, iPad, or iPod touch with iOS 11 or later: Tap Settings > Accounts & Passwords > App & Website Passwords. Use Touch ID when you're prompted.