LDAP is a bit on the weird side... You should take a look at this article and familiarize yourself with the concepts, but they should have an IT person that can provide all the necessary information. It's basically asking for the name of the LDAP group that all the users belong to and a user with permissions to query the LDAP server.
Thanks for the info. Ya, it some sort of needing some LDAP programming. So the customer end up choosing Windows Login as the login method of theirs.