The SCB-68 should have shipped with a big sticker designed to fit under the top cover. Apply the sticker. Now if you look, you should see where the counter-timer connections need to be made on the screw terminals. Consult the DAQ documentation that should have been installed from your NI-DAQ CD for the definitions of the vairous pins. Make sure you only connect TTL (0-5 V) signal levels to the counter-timers. They can be damaged more easily than the analog input channels, or so I've seen.
Also, you might want to post the question over in the Multifunction I/O group.
Dan Press
www.primetest.com