Got an Iphone but...

I got an Iphone a while back and I've attempted to unlock it a couple of times but have been unsuccessful. It was given to me by a friend who isn't too techno savvy and has no clue what version of firmware it. It's NOT a 3G because she gave me her old one to make room for her new 3G. The only thing I can do is "slide for emergency".
Someone told me he could do it but I needed to buy a chip first. I'm pretty sure it's possible to make it work as a T-Mobile phone without the aid of a chip. I don't have access to an AT&T sim either.


To be quite honest, I don't really know what I'm doing and kinda afraid of permanently screwing it up. I'm authentically asking for help as a n00b who hasn't a clue what he's looking at for anyone who willing to help.

Thank you for your time :)