Configure a dialup account in OS X
Open the System Preferences window, and click on the Network icon. The network window should appear as shown below,

Make sure that the “Location” is set to “Modem”, and “Show” is set to your modem (in this case an internal modem). Click the PPP tab, and fill in the form as follows:
The service provider is the name of your ISP (Online Door County, RickNet, etc.)
Your account name is the username given to you by Online Door County
Your password and telephone number is also supplied by Online Door County. Enter them in the appropriate boxes.
The alternate phone number is optional, but if you prefer to enter one, we at Online Door County will provide you with one.
If you would like to save the password so you don’t have to type it in every time you connect to the internet, check the “Save password” box.
Finally, hit the “Apply Now” button to save your changes. You’re done!