on Linux/KDE, how do I let someone see my active screen?

[Derek at CD Baby]

Hi VNC gang - I hope someone can help.  I'm stuck:

I've set up a VNC server on a Windows box before, so that
someone remote can see what I'm doing (or control my mouse)
on my Windows box.

It's been working fine for a year with realvnc.

Now I'm trying to do the same thing in Linux/KDE.
(Let someone see my active screen - same thing I see.)

But it's only starting a NEW X11 window/session/server.

How can I get the unix vncserver to show my existing window?