How do i found out which version of KDE I have ?
Just open any KDE app (e.g. Konqueror, Kate, Kpaint etc.) and click on Help | About KDE
and it will tell you what version you have. You can also open up the KDE Control Centre and it will tell you on the first page.
To upgrade go to http://www.kde.org/download
It's a pretty sizeable download though (if you get all the packages)