Earlier we used to have patterns, passwords and pins to secure our phone, in addition to those Fingerprint sensor is the latest security which is now available in most of the smart phones. This is one of the greatest feature in Moto G5 Plus too.
To set your Fingerprint, follow the below steps:
Go to Settings -> Security -> Fingerprint, here you need to draw a pattern so that at any case your Fingerprint doesn’t work you can draw the pattern and start accessing your phone. So draw the pattern and click Add fingerprint.
On this screen it will ask you to keep your finger and tap it multiple times until it recognises your fingerprint. Once done you can start unlocking your phone with your Fingerprint. Anyone can lock your phone with their Fingerprint, not sure it’s a feature or a drawback.