Pair your MBP and your phone through the Bluetooth utility, by clicking on the icon and going to preferences. Follow the instructions about using the phone as a cell phone. You will notice that your Bluetooth tab under Internet Connect will have a user name, password, and phone number dialog. After that it's pretty easy:
If you have Verizon:
Have the phone dial #777 (dont try manually dialing the phone itself...the number activates the modem on the phone and can only be dialed by the computer)
the user name is your
number@vzw3g.com (area code included, no underscores or dashes, etc.)
password is "vzw" (without quotes)
as i mentioned earlier if you dont subscribe to 3g or EV, then you'll have to force the phone into 1x mode.
if you have any problems post them up and i'll try to help. Or you can look up forums. There are a lot of threads about this.