Activation lock

You will have to enter the AppleID and password used to set up activation lock. If you don’t know that login and password, there is nothing you can do. There is no mechanism to bypass activation lock.

If you bought it used from someone, they need to used their Apple ID and password to turn off the activation lock. If they won't/can't do that, then your phone is good only as a paperweight or a doorstop. There is no other way to get past the activation lock other than entering the Apple ID and password of the person who locked it. Great theft deterrent. Very important to actually verify there is no activation lock set before handing over one's hard-earned money.

It states exactly what to do on the screen.