Windows 10 allows you to automatically lock your computer or tablet when you step away from it. With the Outlined steps below, you will be able to lock your Windows 10 PC or laptop anytime you are away as long as you have a smartphone.

At first, you need to pair your computer with your smartphone via Bluetooth. Then select the Start button on your Windows device and go to Settings > Accounts > Sign-in options.

check Under Dynamic lock, select the “Allow Windows to automatically lock your device when you’re away” check-box.

The computer will automatically be locked after about one minute if the Bluetooth connection between the computer and the mobile device is broken.

Although, the range of Bluetooth varies depending on the device but generally it’s around 10meters
You may also check the alternative steps Below.

Follow The Steps Below;
https://myguideout..com/2019/06/how-to-lock-windows-10-pc-with-smartphone.html