I found a iphone from sprint i looked and looked for owner but no luck?

How would i unlock it to use it?

You need to turn it in to a Sprint location or the police department, because if you attempt to use it you can be arrested for theft, even though you found it.

You did not find it you stole it! Now you want someone to tell you how to break the lock. If you did not steal it, then turn it over to the police.

The owner's phone number is on the phone. Call the owner and return it or turn it in at any Police Station. You would feel better.

Take the phone to a Sprint store. They will reunited the phone with its owner.