Thank you for pointing me in the right direction.
On the ACS site under "documentation", "openacs 5.1.x", "installed packages" "authentication", "installing LDAP support" install auth-LDAP OpenACS service package" then "install" link. Permissions aren't granted to get to documents.
The option #1 above that also takes me to Oscar Bosilla's site but there is no installation information there either.
Under 'uninstalled packages' there is a link for "ACS LDAP authentication where I also looked for information. That link takes me to white papers but no installation information.
Thanks again !