you can do "startx" or "kdm" in order to enter in graphical mode,
but if you want to enter automatically every time you boot, then you should change the file "/etc/inittab"
In "/etc/inittab" you have to select "4" as the default runlevel, something like
# Default runlevel. (Do not set to 0 or 6)
If, when you do that, your system boots into gnome, and you like kde, what you have to do is change "/etc/rc.d/rc.4" to
# Tell the viewers what's going to happen...
echo "Starting up X11 session manager..."
# FIRST KDE:
if [ -x /opt/kde/bin/kdm ]; then
exec /opt/kde/bin/kdm -nodaemon
# THEN GNOME's gdm session manager:
if [ -x /usr/bin/gdm ]; then
exec /usr/bin/gdm -nodaemon
# If all you have is XDM, I guess it will have to do:
if [ -x /usr/X11R6/bin/xdm ]; then
exec /usr/X11R6/bin/xdm -nodaemon