CiviCRM + Wordpress + Contact 7, how to get it to work
You must also install a CiviCRM extension on the other end - see this blog post for details.

Note that this plugin is NOT very mature, and isn't recently updated.  Its killer feature is the ability to post data to a remote CiviCRM.

If the CiviCRM you're trying to post to is installed on the same WordPress site, then you'll want to use Caldera Forms with its CiviCRM integration.  This is the plugin of choice for CiviCRM/WordPress developers and is receiving active support.