Two packages are available within the synaptic.kde-desktop and kubuntu-desktop.Latter is a stripped down version of the original and is streamlined.We recommend kubuntu-desktop instead of kde -desktop.

To install,simply  follow the steps

• Goto system-->administration-->synaptic package manager and search for the package kubuntu-desktop.Mark it and then apply the changes.
• OR you could simply goto applications-->accessories-->terminal and type the following

                     sudo apt-get install kubuntu-desktop

• The system will ask you if you want to use kdm or gdm. gdm is recommended.

Content Courtesy: http://www.ubuntuguide.org
Content License:http://www.gnu.org/copyleft/fdl.htm