How do I get rid of the passcode or reset the entire phone?

I'm setting up a secondhand iPhone 5. After entering my iCloud details for restoration, it attempted to restore but kept turning off and restarting. When the restoration finished, the phone resets and is now asking for a passcode but it keeps saying I'm entering the wrong passcode. I've tried previous passcodes from my old phone and tried to connect to iTunes but the new iPhone isn't visible. I haven't set up Find My iPhone either. How do I get rid of the passcode or reset the entire phone?