Connect your Mac to the Internet using a dial-up modem
You can set up a dial-up modem using Network preferences.
On your Mac, choose Apple menu
> System Preferences, then click Network.Select your modem.
If your modem isn’t on the list, make sure it’s connected to your Mac (either internally or externally), then click the Add button
at the bottom of the list. Click the Interface pop-up menu, choose Modem, give the modem a name, then click Create. Enter the settings provided by your ISP, such as the access phone number, your username and your password.If you have configurations for different accounts, click the Configuration pop-up menu, then choose the account you want to connect to.
You can add or edit configurations using the pop-up menu.
Click Connect.
If you select “Show modem status in menu bar”, you can use the modem status icon to connect. Click the icon, then choose Connect.