Use
'taxonomies' => array('post_tag')
in your
register_post_type()
when registering an arbitrary type of posts.
Here is a good example of open spaces:
register_post_type('movies', array( 'labels' => array( 'name' => 'Movies', 'singular_name' => 'Movie', 'menu_name' => 'MOVIES', 'all_items' => 'All Movies', 'add_new' => 'Add A Movie', 'add_new_item' => 'Add New Movie' ), 'public' => true, 'supports' => array( 'title', 'post-formats', ), 'show_in_admin_bar' => true, 'taxonomies' => array('post_tag'), ) );