There is no admin section.
There is no user signup section.
This is not an open email system.
This is a front-end to already implemented IMAP servers. So to log in, you have to have users that are already created on your system (by cPanel, Plesk, VHCS or whatever hosting control panel you have) and your system needs to have an IMAP server running (Exim, Courier, Dovecot, etc.). Then users can log in using their email address and Password for that email address.