These settings go into System Preferences under the Network area. You have to add a Bluetooth device and pair the phone with modem. If you don't know how, read the forum post that got me this far. The forum works great with Tiger but did not work with Leopard. I had to make changes to the Advanced area to get it to work properly.
Username: PHONE_NUMBER@vzw3.com (not sure how important this is, I've done it with the BlackBerry Internet Server username also)
Model: Dialup Device
(Leave the rest as defaults)