Your Plesk control panel is accessed at http://{domain}:8443/
i.e. if your domain was designRweb.co.uk then your Plesk CP logon would be at ...
http://designRweb.co.uk:8443/
You do not need to (and possibly cannot) access it by IP address.
The control panel information is encrypted with SSL, but it is a standard application self-signed certificate which may give you a security error to acknowledge first.
If you view the certificate (issued under name plesk) and then install the certificate, you will bypass the security message on all future visits.
