As far as finishing the AD authentication part, you will need to go into the Active Directory server group via ASDM and add the Administrator account and password. This will be illustrated in the document links provided below. Also, I have attached a link to doing LDAP maps, which will allow you to restrict access to VPN through a group assignment in Active directory.
Configure Server Group and Add servers:
http://www.cisco.com/en/US/products/ps6120/products_configuration_exampl
e09186a00808c3c45.shtml
Configure LDAP Map:
http://www.cisco.com/en/US/products/ps6120/products_configuration_exampl
e09186a00808d1a7c.shtml
<http://www.cisco.com/en/US/products/ps6120/products_configuration_examp
le09186a00808d1a7c.shtml>