Icloud will not pull up mail

I have a macbook (Mac OS X Lion 10.7.4). I can not pull up my email in icloud! When i go to mail preference this is in my incoming mail server

( po2-imap.mail.me.com ) it is in light grey and will not allow me to change it. Someone please help me. Do I delete this account and start a new one? If I delete it will i lose all my mail?