# These are the default runlevels in Slackware:
# 0 = halt
# 1 = single user mode
# 2 = unused (but configured the same as runlevel 3)
# 3 = multiuser mode (default Slackware runlevel)
# 4 = X11 with KDM/GDM/XDM (session managers)
# 5 = unused (but configured the same as runlevel 3)
# 6 = reboot
# Default runlevel. (Do not set to 0 or 6)
Depending on your distributor you want the number beside the X11.
In Slackware it's 4, but other distributions its 5. So, you'll want to change the 3 to to either a 4 or 5.
If you're using VI to edit the file move you cursor over the "3" hit the "x" then the "i" then insert your number 4 or 5. then :wq Next time you reboot it'll boot to X.