By default VPS servers just have the operating system with root access. To add cPanel you would need to login with a ssh program like Putty. Once you log in, you need to install two things.
1. You have to update the OS like this: (Make sure and choose yes when it asks for approval)
yum groupinstall base2. Install cPanel: (This takes about an hour or two to install depending on the speed of your VPS or server)
Once it's installed, you will be able to access it by adding /whm after your IP
3. In some cases the server will block you after installing cPanel. If this happens please go here on how to unblok servers and access:
How to unblock your server