starting xwindows apps from console?

[Dragoncrest]

I know I saw something about how to do this at one time, but I can't
seem to find any information about it anymore.  What I'm looking to do
is start several KDE gui based apps from a remote ssh session.  I can do
it from the actual machine via the console because it knows how to find
the running Xserver and selected desktop. But if I'm remotedly shelled
in via SSH, it has no idea where Xwindows is or if there's an active
desktop or KDE session going.  I do remember one time seeing an example
of how to do this that was something like "/path/to/app/appname :0 d1"
or something along those lines.  This would then allow me to start a gui
app in KDE (provided it was running) via my remote shell.

Does anyone know the exact command to make this work?  It would be
useful for me if I'm doing remote troubleshooting for any of my friends
and family where I need them to use a particular gui app, but I don't or
can't get them to navigate over and find it.  (yes, I have friends and
family using bsd and nix who are that clueless, but at least they're
using nix now instead of windows.  hehe)