There are two ways to connect your interner using bluetooth connection.
1.You can use the phonr as a modem for a dial-up connection to the internet service provider.

2.You can pair phone with your pc then using gprs you can make your computer accessible to internet.
 

Most of the phone doesn't have the in built feature of acting as a moddem so i am going to explain the second method today.

1.Open Buletooth Setup Assistant, in/Applications/Utilities.
2.Now pair the phone and the computer.
3.Select the option to Access the Internet with your phone's data connection, as shown below.
4.Enter the connection setting information. If you are not sure what username, password, or other information needs to be entered, check with your mobile phone provider or your ISP for more information.
5.Finish the Setup Assistant, and then the phone should be ready to connect.