On your Mac, choose Apple menu  > System Settings, then click Touch ID & Password in the sidebar. (You may need to scroll down.)

Open Touch ID & Password settings for me

Click Add Fingerprint, enter your password, then follow the onscreen instructions.

If your Mac or Magic Keyboard has Touch ID, the sensor is located at the top right of your keyboard. You can add up to three fingerprints to your user account (you can save up to five fingerprints on your Mac).

Choose how you want to use Touch ID:

Unlock your Mac: Use Touch ID to unlock this Mac when you wake it from sleep.

Apple Pay: Use Touch ID to complete purchases you make on this Mac using Apple Pay.

iTunes Store, App Store, and Apple Books: Use Touch ID to complete purchases you make on this Mac from the Apple online stores.

Autofill passwords: Use Touch ID to automatically fill in user names and passwords and to automatically fill in credit card information when requested while using Safari and other apps.

Fast user switching: Use Touch ID to switch between user accounts on this Mac.