If you visit http://www.xerox.com/suport and type in the 7435 you will get to the KB and you will be able to search for Xerox Standard Accounting. Since it sounds like you have mutilple machines on your network you may want to look at a software solution to track/monitor all of your output devices.
I can suggest a product like Print Audit or something similar.
The feature you are talking about is called Xerox Standard Accounting(XSA)
Go to this link and download the System Administrator Guide:
The info you need begins on page 170.
We have a workcentre 7345 and I'm trying to figure out how to set it up so people need a code to make copies and so we can track who is printing. Please advise.