There was a lot of confusion about how to set this up on our phones. Here's a post to try and head off a bunch of posts about it. Make sure you already have a screen lock setup. You wouldn't believe how many people tried to set this up without that on first. You can't set up Trusted Devices if you have no screen lock. Go to SETTINGS > SECURITY. Scroll way down under ADVANCED. Click TRUST AGENTS. Turn on SMART LOCK (GOOGLE) Now the SMART LOCK setting will light up under that same SECURITY section. Go there to Configure Trusted Devices and/or Places.