Home switch testing?

Hi, I just received some slotted opto sensors
that I was planning on using for home sensors
on my retrofit.
This is where I got them from.

http://www.allelectronics.com/cgi-bin/category.cgi?
category=435&item=OSU-50&type=store

They have 4 leads on the bottom two are for 6 volt
power + and - and the other 2 are suppost to be
a normaly closed switch wich is disrupted when a
deflective object is penetrating the slot.
With my obvious limited knowledge about electronics
I tryed to hook the sensor up to test its function
using a couple of D cell batterys a 6 volt powersupply
a small voltage lightbulb and a multytester for electronics.
I have not been able to get this sensor to do any kind
of verifyable disruption yet.
I tested on 2 of the leads was continuety so I figured
this must be the switch side.
Testing to disrupt the lightbulb did not work in any of the
various ways I tryed to set this up.
Could any of the more electricly gifted persons please point
out what I am doing wrong here.
I suspect this may not work the way I think it would.
The 2 sensing leads are suppost to be hooked up on 2 pins
of the Parallel port of the PC, have not tryed this yet.
How could I set this up for testing.