Click on the Apple icon and then click on System Preferences...
Click on the Network icon under the Internet & Wireless section.
In the section to the left, click on your modem.
(The example here says USB Modem - Not Connected)
Telephone Number: Type in the number that was given to you.
Visit our Access Number page to locate a number near you.
Account Name: Type in your username.
Password: Type in your password.
Place a check next to "Show modem staus in menu bar"
When finished, click the Connect button.