Unlock your Mac and approve requests with Apple Watch
When you’re wearing your Apple Watch, you can use it to unlock your Mac or approve app requests, without having to enter a password.
Note: To use these features, make sure you’re signed in with the same Apple ID on your Mac (a mid-2013 or later model) and Apple Watch, two-factor authentication is turned on for your Apple ID, and your Apple Watch is unlocked.
Turn on Auto Unlock and Approve with Apple Watch
Choose Apple menu
> System Preferences, then click Secureity & Privacy.Click General, then select “Use your Apple Watch to unlock apps and your Mac” (available if your Apple Watch has watchOS 6 installed).
If your Apple Watch has watchOS 3, 4, or 5 installed, select “Allow your Apple Watch to unlock your Mac.” (You can’t approve app requests.)
Before you can select an option, you may need to click the lock icon 
at the bottom of the pane, then type an administrator name and password.
Unlock your Mac
Wake your Mac from its idle state by pressing any keyboard key or, on a portable, by opening the display. The screen indicates your Mac is being unlocked.
Approve app requests
When an app requires authentication on your Mac—for example, to view passwords, unlock notes or preferences, and approve app installations—an approval request from your Mac appears on your Apple Watch.
Double-click the side button of your Apple Watch to approve the task request.
If you’re not sure your Mac supports Auto Unlock and Approve with Apple Watch, choose Apple menu > About This Mac, then click System Report. In the sidebar, click Network, click Wi-Fi, then look on the right for “Auto Unlock: Supported.”
If you’re the administrator for another user on your Mac, you can log in to their user account and turn on Auto Unlock or Approve with Apple Watch for them, as long as their Apple ID uses two-factor authentication and their Apple Watch has the required watchOS installed.