http://www.advancedcustomfields.com/resources/acf-fields-post_object-query/
The arguments value is the same as that used for WP_Query http://codex.wordpress.org/Class_Reference/WP_Query
One warning though, if the post type is hierarchical then the displayed posts will can end up broken. As far as I know it will only work 100% of the time for non-hierarchical post types.
