Assuming you have made a user account for yourself, log in as your user and type:
and see if you get a desktop. If you have not made a user account, you'll want to do that first, unless you plan to start X as root and make your user account from root's desktop.
I have a Bluewhite64 disc here but haven't booted in in a long time; but if I remember right, it's the same as Slackware in that it starts/installs configured to start in runlevel 3 out of the box.
Edit /etc/inittab if you want it to start in runlevel 4 (the graphical level). Edit the line in the file as follows:
# Default runlevel. (Do not set to 0 or 6)
In yours, the 4 is a 3 so change it to a 4.