Then create an .xinitrc
file and add one line to it, telling X to load KDE, as follows:
$ echo "exec startkde" > ~/.xinitrc
startx should (hopefully) load KDE when called.
And if I may add.. don't ever login as root into a graphical desktop environment, because it allows for mistakes to occur without anyway of recovering them. You should create a user account, and use it as your main account. You should only need root to do maintenance, checkups, or edit system-wide files, and the like - NOT as your default account. It is considered bad practice and leaves your computer vulnerable to attacks, as any program that is run by root is given root permissions which allows it to run other processes with the same access rights.