Click on "Expanded Settings" at the bottom of the page and then on "Smart Lock". You may also just type "Smart Lock" into the search field on the Settings page to quickly locate it. Select "Smart Lock configuration" from the "Smart Lock" menu. You must re-register using your password on your Chromebook. This prevents others who have access to your Chromebook from connecting it to their phones. You must know your password in order to connect it to a phone.
