How do I access my Plesk control panel?

You can log into Plesk by pointing your browser to https://example.org:8443 (replace example.org with a domain pointed at your server). This will take you to a login screen where you can enter your username and password.

If you are prompted regarding an untrusted connection, then this is because the SSL certificate is self signed and your browser does not accept self signed SSLs by default.