Configuring and Connecting to your Dial-up Connection
Configuring your dial-up connection requires that you set up your modem using your Mac's networking utility. To do this, click "System Preferences" on the Dock and click "Network" under the "Internet & Wireless" heading. This launches the networking utility and displays a list of the connections your Mac can use.
Select your dial-up modem from the list on the left pane to view a configuration pop-up menu. Click "Add Configuration" and enter all of your ISP's information, including login credentials and dial-up phone number in the applicable fields. Click "Save Password" if you want to remember the password in the future. At this point, you should be able to connect to the Internet unless your provider requires advanced settings. If advanced settings are necessary, click "Advanced" to view the additional settings.
Unless your provider specifies that you need to use DNS server addresses manually, you'll likely not need to do anything on the "Advanced" section. If you do make any changes, click "OK" to return to the main connection screen, then click "Apply" to save all your settings, including the login information.
Now that you're set up, you can connect to the Internet. Simply select your dial-up modem from the list in the networking utility, then click the "Connect" button to dial in. If everything goes well, you should be able to view Web pages in Safari or connect to iChat. If something goes wrong, check out Apple's Dial-up Troubleshooting page to fix any potential problems.