[Koha] new to koha: where to get z39.50 servers?

[H.S.]

Hello,

I maintain a little bunch of computers in a local community center. They
wanted to make a catalog of all the media and books that they have in
their little library (a few thousand books). I am learning about library
management stuff as I go along ... and only as much as I need to know
for installing Koha.

I have installed Koha on Ubuntu Feisty (soon to be upgraded to Gutsy). I
am wondering, how do I add Z39.50 servers? Do I need any kind of
authorization to connect to various such servers (username and
password)? Are there any open ones?

thanks for all the help,
->HS