How do I find my Apple ID for my iPhone 5C

How do I find the Apple ID for my iPhone 5C? We cannot remember it and we never wrote it down. It was my daughter's phone and she got a new iPhone and no one in the house can remember the Apple ID. Through iTunes I did a total Reset, but it is asking for the Apple ID and password to activate it. Looking for direction we need to go to activate the phone. Want to use it for WiFi apps & Internet. Thanks for any help.