It is possible to do LDAP authentication without importing AD
- just follow Vikrams post.
Note the LDAP is against AD and that the LDAP credentials can be your own to test: latter, make sure you have a user account for SEPM (unless the AD allows anonymous bind).
Note also that the "username" is a long LDAP username, not your short domain\user or user type (make sure you know the format of your username in ldap)
for exampe, cn=My Name,ou=user,dc=company,dc=org (or something like that)