I recommend you to jailbreak it tethered using redsn0w 0.9.15b3 before you do this, do this at your own risk I'm not responsible fot your device (check through my posts and you may find the thread) and then simply open iExplorer go into the applications folder (you may have to look for it) and then hop into there and delete setup.app and then reboot using redsn0w and just download 'Evasi0n untethered' from Cydia and you have got past the Activation screen forever on iOS 6.x and have a jailbroken iPhone!
Many thanks,
Software