You will need the server settings for your e-mail address. Go to EarthLink Server Settings to get these settings.
Open Mail from the Dock or Applications folder.
If this is the first e-mail account you're setting up, the "Welcome to Mail" assistant may appear. If so, click Continue. If not, click File and select Add Account.
Select the Accounts icon in the toolbar of the Mail Preferences window that just popped up. Then select your EarthLink e-mail account.
Exit out of the Mail Preferences menu and you're now ready to send and receive e-mails.