Although I do not use Kubuntu (I use the much simpler, lighter, and faster Lubuntu), Kpackagekit should already be installed under: Kmenu > System Settings: https://help.ubuntu.com/community/Repositories/Kubuntu
I would recommend just using Synaptic Package Manager in Kubuntu though. It is a more robust and trouble free package manager for the *buntus; and it is installed across all the K/X/L/Ubuntu versions. Although Kpackagekit is said to be "improved" in Kubuntu 11.10:http://www.kubuntu.org/news/10.10-release
it has had it's share of issues in previous Kubuntu versions.
Here is a good and easy tutorial to follow for installing Kubuntu 11.10 and installing apps on it: http://www.howtoforge.com/the-perfec...-kubuntu-11.10
Write back if you need more help.