Go to Time warner and on their local web site hunt around for the email server settings. Write them down if need then open Mail. In the Mail menu item "Mail" the drop down (when you click on the menu item "Mail") and select "Preferences". When the "Preferences" open up select the menu item "Accounts" and set up you email account to the way the Warner web site told you to use for email servers.
Not every Mac user uses time Warner so you have to find your local ISP email server settings so you can setup Mail.
Now if ail is not opening at all, keep open the email settings web page and quit Mail. Then go to the folder /Users/Your UserName/Library/Preferences/ and find the file com.apple.mail.plist to take to the desktop. Then launch Mail and use the Mail Preferences, Account to re-setup the server settings. You will not loose the saved email that you have so don't worry. The important thing to know that you must fist find and know the email server settings because you will have to put them back into Mail. however Mail will reset but keep you old saved email (if they are in folders).