Rebooting it with out remembering the info I used when I set it

Rebooting it with out remembering the info I used when I set it

I bought all three of my kids one of these phones at the same time well I set them up of coarse I don't remember what email or passwords or any of that I used my daughter locked herself out so I master reset it but it still wants the Google address synced with the account I still have the boxes I bought them in please help.