unlocking phones

Carrier Lock:- Though your iPhone’s original Carrier is not obligatory to unlock your iPhone, but you may know the process here --> How to unlock your iPhone for use with a different carrier ...

Activation Lock:- If it is Activation locked, read here --> Activation Lock for iPhone, iPad, iPod touch, and Apple Watch ...

If you mean that you need an Apple ID and passcode, then you contact the person you got it from. If they won’t or can’t help you, return it for a refund. You will never be able to use that phone.