Welcome to the forums.
You'll have to ask your administrator what the address of your mail server is. From you example of
my.name@myschool.org the server maiht have a name of 'mail.myschool.org' but that depends on what they've named it.
As for POP or IMAP, Zimbra supports both but it will depend on whether they're enabled. Your server admin should have told you all this.