The first link is where I think you should manage the subscriptions that this thread originally talks about.
Second link, is to the email user interface "squirrelmail", an interface I prefer, but I don´t think it can handle the imap settings.
Third link, is basically a cPanel lite version of the webmail combining login´s for both Horde and Squirrelmail.
On all of them you should be able to log in with any real email address you have set up in cPanel.
If you are receiving errors when trying to enter anyone of them, please submit a ticket and the techs will look in to it.