see here:

2) Once you have IIS setup and is working and directs to the passagepoint website, open IIS manager, and click on the passagepoint site > double click on Authentication

Enable "Anonymous Authentication" and disable everything else

3) Login with an Admin user and configure Directory Link to use LDAP

This KB has docs for both either using normal LDAP or LDAP over SSL 

4) Designate The directory Link you've just configured above to the web module interface

5) create the authentication rule as LDAP (these settings are very similar to the directory link and you can use the same doc)

6) Designate LDAP as the authentication method to the wi1 website