Registrando post type plugin

index.php

<?php
function post_type_flexslider() {

  register_post_type( 'flexslider',

  array( 'labels' => array(
  'name' => __( 'Flexslider', 'andres-dev' ),
  'singular_name' => __( 'Flexslider', 'andres-dev' ),
  'all_items' => __( 'Todos los sliders', 'andres-dev' ),
  'add_new' => __( 'Agregar nuevo', 'andres-dev' ),
  'add_new_item' => __( 'Agregar nuevo slider', 'andres-dev' ),
  'edit' => __( 'Editar', 'andres-dev' ),
  'edit_item' => __( 'Editar slider', 'andres-dev' ),
  'new_item' => __( 'Nuevo slider', 'andres-dev' ),
  'view_item' => __( 'Ver slider', 'andres-dev' ),
  'search_items' => __( 'Buscar slider', 'andres-dev' ),
  'not_found' => __( 'No se encontraron resultados', 'andres-dev' ),
  'not_found_in_trash' => __( 'No se encontró nada en la Papelera', 'andres-dev' ),
  ),
  'public' => true,
  'menu_position' => 2,
  'menu_icon' => 'dashicons-images-alt',
  'supports' => array( 'title', 'thumbnail')
  ) /* Fin de las opciones */
  ); /* Fin del registro post type */

}

add_action('init', 'post_type_flexslider');