How do I insert a SIM card into an iPhone?

I just got an iPhone from my dad, but it had his SIM card in it. I've read something about them being %26quot;unlocked' and if that's the case, one cannot change the SIM card.



I'm assuming that you need a password or something to make this work. I think my dad knows it. So the question is, how do I get to that specific page and how do I physically remove his SIM card and put mine in? I'd greatly appreciate any help. :)How do I insert a SIM card into an iPhone?
You can search google for a software to unlock the phone, as for taking out the SIM card it is different on the iphone than most phones. You must eject the SIM tray. On the top of the phone there should be three things the headphone jack, the sleep/wake button, and a little hole in between the two. you have to get something small and pointy like a paper clip and stick it in that little hole, then a tray should eject and the SIM card sits on that.