If you don’t have a Unlocking method you should set a Secure unlocking method for your Device Before Setting up Face unlock. Open Android Settings find Security section Tap on Screen Lock Select any one from Pin, Password, or Pattern unlocking methods. Follow the instructions and set up your unlocking method.
Once you return back to the security settings Page, Choose Smart Lock and Enter your Unlock Pattern when Prompted .now Tap on Trusted Face then you will see some information’s about unlocking your Device with your Face. Read the information very carefully and Tap set up when you are ready.
Before the Process make sure you are in indoors or not in a overly bright area. This will help Android to capture your Facial features. Once you selected a good spot tap next. Now your Mobile will start the process of detecting your face. Hold your Device at eye level to match your face with the ring of dots onscreen.
After you have positioned your Mobile and face properly, the dots will start to turn green. Wait until All dots to turn green and a tickmark will appear in the center of the Screen. When you see that tap Next.
For better results you have to show Android how you look under different situations such as with short hair, long hair, clean shaven, with mustache, beard, with cap on, with eyewear’s and whatever attribute. This will help to recognize you better when your Appearance changed.
To Do that Go to Settings and Tap on Security, Select Smart lock. Then tap on trusted face and select improve face matching. Move to a Spot that has different lighting. And change to a different Appearance. Then tap next and repeat the method of adding a face. You can do this Process as many time as you want.
Note: face unlock is not very popular among Android Users. There is some reasons for it first anyone can hack it without any Programs with your Photo Anyone can Unlock your Phone. Second Face unlock doesn’t work Good in the dark and Overly bright location.