If Find My iPhone is enabled, you cannot fully factory reset and use the iPhone without the Apple ID password
If you know the iPhone passcode, go to Settings > General > Transfer or Reset iPhone > Erase All Content and Settings
If you do not know the passcode, try using the Erase iPhone option on the lock screen after repeated failed passcode attempts
If prompted, enter the Apple ID password to turn off Activation Lock
If you do not know the Apple ID password, use Apple’s account recovery at iforgot.apple.com
If you have access to the Apple ID on another device, remove the iPhone from the account in Find My
If the iPhone is disabled or locked and you do not have the password, you will need a computer to restore it
If you cannot use a computer, contact Apple Support or visit an Apple Store or authorized service provider