V551 Questions

I am verrrrrrry new to this newsgroup so I maybe asking questions that have
been asked before but here goes.
I need to know what it means to unlock a phone.
I have a V551 that has the smart card in it but is "unregistered SIM".
I had originally got it for the camera from a friend that "found it" at a
strip bar in a different town. He wiped out all the info in the phone so I
don't know anything about it.
Anyway, I want to maybe use it now, so I need to know how I can start using
it.

I need to know if I can "unlock" the phone so that I can call Cingular to
start using it
and if anyone knows any tricks, tips, and/or hacks for the V551

Thanks in advance