To log into the Plesk Control panel, you need to navigate to the server using a Web Browser. The way you do this depends on if your server has a hostname or not. Please note that in both cases you need navigate to port 8443 to access the control panel, this is done by adding a colon followed by the port number 8443 in your web address.

METHOD 1
If you only know the IP address of your VPS and have not configured a hostname on your VPS, you can navigate to the login page using the IP address. The path will look like this: https://<PublicIPAddress>:8443. Here is an example: https://123.123.123.123:8443

METHOD 2
If you have previously configured a hostname and domain for your server, you can navigate to the login page using that hostname. It would look like this: https://<hostname>:8443, and here is an example: https://mycontrolpanel.domain.com:8443.

You have successfully accessed the login page when you see a login page that looks like this: