Windows 10 Using Dynamic Lock

Note, Dynamic Lock is a feature of Windows 10, Version 1703, the Creators Update. If you currently do not have the Creators Update you can download and install the update from Getting the Windows 10 Creators Update.
What is Dynamic Lock
A new feature of the Windows 10 Creators Update is Dynamic Lock, which allows you to pair your smartphone (using Bluetooth) to your computer. Once paired if you walk away from your computer your computer will automatically lock.
Note, it will not automatically unlock the device when you come back to your computer. Currently, if you want this functionality you would need a MacBook, which you can pair with an Apple Watch and once you come back to your MacBook the MacBook will automatically unlock.
Pairing Your Smartphone With Your Windows 10 Computer
A must prerequisite for this functionality is of course Bluetooth. Your device will need a built-in Bluetooth adapter, or you can buy an external Bluetooth adapter for a desktop if needed.
External Bluetooth Adapters such as:
Pairing
Click on Start > Settings
Within the Settings Window click Devices > Bluetooth & Other Devices > Add Bluetooth or other device
Add a Device window click on Bluetooth
Ensure your smartphone's Bluetooth functionality is turned on. You will be navigated to the Bluetooth discoverable window. If your smartphone is not discovered at first try turning your smartphone's Bluetooth off for 5 seconds and then back on.
Once your device is discovered (the device name should show), click on the device and ensure the pairing codes are correct on each device and press Connect.
If paired correctly, Paired should show under the device name, click Done.
Now your smartphone should be paired with your computer.
Activate Dynamic Lock
Click on Start > Settings
Within the Settings windows click on Accounts.
Click on Sign-in options
Scroll down to Dynamic Lock and place a check mark beside Allow Windows to detect when you're away and automatically lock the device
Now you have successfully setup the Windows 10, Version 1703 Creators Update Dynamic Lock feature.