You need to have a phone running Android 5.0. Get it and turn on Bluetooth, then grab your Chromebook and power turn both on. On the Chromebook:
1. Go to Settings
2. Click on ‘Show advanced settings’
3. Under the heading “Smart Lock (Beta)” click on “Set Up Smart Lock”
You will then have to log in with your password again, then it will take you to the desktop of your Chromebook and a “Let’s get started” box will pop up. It will guide you through the last steps of pairing your phone/Chromebook, and Smart Lock should work after you finish.