The ubuntu desktop will by default install gnome desktop, if you are looking to install the KDE desktop. You may want to look elsewhere for that information.
INSTALLING UBUNTU DESKTOP
Connect to your VPS using SSH, and run the following commands:
sudo apt-get update sudo apt-get install ubuntu-desktop sudo chmod -x /bin/plymouth sudo reboot
Your VPS will now reboot into the standard Ubuntu desktop. In the following steps you will learn how to access it.
SETTING UP VNC FOR REMOTE DESKTOP
Connect using the Rescue Console
(You should see the desktop)
Click System -> Preferences -> Remote Desktop (Enable Remote VNC Access)
Setup the Security (A Secure Password is Highly Recommended)
You should now be able to connect to your VPS via your favourite VNC viewer using the VNC Settings specified using the rescue console.