For simplicities sake (I'm tired), you can open a console, locate kedit, then su to root. This is assuming you've got permission as your user to su as root (in some distros you have to be part of the 'wheel' group, or enable permission in kde/gnome). Then, type the full path to kedit (ie., /usr/bin/kedit or similar). The reason is probably that your distro disables paths for your root user (for security reasons), so you can't use a lot of user based programs as root (which you generally don't want to do anyway).
Adding the ampersand after the program will free up your console:
# /usr/bin/kedit &
another way to do this is to use the '-c' switch with su, which just runs a single program with root permissions.
Hope this helps.