for MacOS X

Launch Mail from the Dock.

Once Mail is running, open "Preferences" from the "Mail" menu and select the "Accounts" tab.

Click the little "plus" icon to create a new account. Change the account type to "POP3". Fill in the rest of the fields per this example:

Email Address:
Full Name: John Smith
Incoming Mail Server:
Outgoing Mail Server:
Incoming Mail Server:

Choose the Server Settings button and set "Use SSL" and change Authentication to password. Set the User Name and Password fields to the same Username and Password you used for the incoming mail server.

Click on the advanced tab and select the "Use SSL" checkbox.

Close the Preferences pane and Mail will connect and fetch your mail.