I do mine with the USB cord, but apparently you can also use Bluetooth if you have it. I've never attempted it with Bluetooth, so I have no idea how well it works.
If you know someone who has a PS3 controller lying around that you can borrow for a couple of days to fiddle with, I would highly recommend that. I don't know how expensive new controllers are down there, but up here they're about $55. And I've heard wired 360 controllers are much easier to "install." They're both Microsoft products (assuming you use Windows). Otherwise, the only surefire method I've seen of using a DS3 on a computer is with
MotionInJoy, which can be... kind of touchy. I've seen Youtube videos of other people setting up their DS3s without MiJ, but I've never been successful in getting those methods to work.