The IMAP server, and the login, will depend entirely on who provides your email address. Is it Gmail? Verizon? BTInternet? Each company will have a different set of servers. For example, for Gmail, you use "imap.gmail.com". Usually you can simply do a web search for "IMAP server" + your mail provider, and the answer should turn up. You can also check within the preferences of any Mail program that you already use (perhaps Mail on the Macbook?) and use the same server details. Make sure you check what the correct port number is, and whether or not you need to use SSL (secure login).
If you get email on your own domain name (eg bob@mycompany.com), you need to check with your hosting company to find out what server name to use.
Matt