You should only install cPanel on a fresh installation. Your VPS needs to have a fully qualified domain name (hostname) in order for cPanel to install correctly. Other minimimum cPanel requirements are described here.

command for the installation: cd /home && curl -o latest -L https://securedownloads.cpanel.net/latest && sh latest

The installation may takes up to 50 minutes. When it finishes, go to http://<your IP>/whm to login and configure cPanel/WHM. By default your credentials are root/root password.

Use sh latest to check any error that could have occured during the installation.