I have not been able to find the data sheet for the shift register you have.

Basically there are three pins on the shifter that need controlled and one sometimes two can be paired up when using multiple shifters. (shifters being in or out).

If I remember correctly, parralax has good documentation somewhere about how to make a shifter work with a stamp.

If someone else does not get to it first, I will dig up a snippet when I get home and post it for you.