[ale] What do I have to install/enable to get X started?

[Jim]

I'm trying to turn a server into a desktop.  I've install KDE and 
utilities, but KDM says no displays available so I'm sure X isn't 
running yet.  Problem is I can't figure out what starts X.  This is a 
Centos system, so I looked through a running FC6 system but there's 
nothing in /etc/init.d that mentions Xorg. 

So what the heck do I need to do to get GDM or KDM running after boot?

Thanks,
Jim.