[CentOS] startx on console 2

I seem to recall that there is some special option to run X11 on <Alt-F2>

On this ClearOS system, their console sits on the default console. You 
have to <Alt-F2> (etc.) to get a text login.  Now that I have Xfce kind 
of installed, I want to see it on the system console, and I thought that 
just running startx would work.

It doesn't.  Got some errors. And then I remembered years back where 
there was some extra options used to run startx on one of the other 
consoles.

But it has been too many years and I can't find any notes on it. The 
manpage says something about a DISPLAY option, but its use is very unclear.

thanks