> How do I start XWindows ?

Either as root "xdm" or "startx"

> How do I add new users ?

cf man vipw
man 4 passwd
(actually, I am not sure of the section number, but you want the
passwd that corresponds to the password file format, not the command
passwd which allows you to change a password)

I have never tried rcm, so maybe someone can say how it is done with that.

I don't know about the keyboard mappings.

Patrick