First download the GNOME Desktop environment to your server:
yum groupinstall "Desktop"
After installed GNOME Desktop enviroment then start to install TigerVNC server
yum install tigervnc-server xorg-x11-fonts-Type1
Now your VNC is installed on your CentOS 6. Now is time to start the VNC server
Now time to connect to your VNC Server:
First download VNC client:
Then use it to connect to your server.