From the Apple support website.
[link|https://support.apple.com/guide/iphone/set-up-touch-id-iph672384a0b/ios#:~:text=Add%20a%20fingerprint,-You%20can%20add&text=%2C%20for%20example).-,Go%20to%20Settings%20%3E%20Touch%20ID%20%26%20Passcode.,Follow%20the%20onscreen%20instructions.|Set up Touch ID on iPhone - Apple Support|new_window=true]
== ***Add a fingerprint*** ==
You can add multiple fingerprints (both of your thumbs and forefingers, for example).
# Go to Settings > Touch ID & Passcode.
# Tap Add a Fingerprint.
# Follow the onscreen instructions.