How to completely erase an iphone 5?

I found an iphone 5 at my group home, th girl left and never returned. When I tried to restore it, it asked for the apple id she had. How do I completely restore it

I've already restored once completely and now when it came to activating it with an apple id. It won't let me log in with my apple id. Is their anyway to completely reset it

I want to remove the apple account but I can't. And if your just going to lecture me to take it back. **** off I didn't ask for all of that. This girl stolen more than half of my belongings and my sons stuff so I have no remorse if she really wanted the iphone she would've came back by now and its been 2 months

If it has iOS 7 then you won't be able to erase it without her password. Thats a security feature to prevent anyone from stealing it.

This is Apple's form of security against lost/stolen phones. If a phone is lost or stolen and is erased, it can only be used once the previous owner's Apple ID has been entered. Otherwise, the phone is bricked and it can't be used or activated. Not even Apple can activate it.

I would highly suggest filing a police report to the girl who stole your belongings.