Upgrade from ubuntu 12.04 to kubunut 14.04 without reintsalling all programs topic

Hello
I have been working on Ubuntu 12.04 for some years and I've installed some programs on it. Now I want to upgrade to Kubuntu 14.04 but I don't want to reintsall all programs. I've downloaded kubuntu installer but don't know how to install it to save my programs.
Thank you