Librarians never lie, but they occasionally make mistakes.
To access the Ebsco Z39.50 server, you will need a username and password which are specific to your institution. Your library will have to obtain these from Ebsco. You cannot authenticate with a personal username and password.
Normally libraries manage access to subscribed databases via a local proxy server, and library users can authenticate on those proxy servers using their local username and password. Unfortunately this procedure does not work with the Z39.50 servers which are used for EndNote connection files.