IN FUNCTIONS.PHP or best way in (IN FUNCTIONS.PHP includes) include/custom-post-type.php

OR USE PLUGIN wp cpt ui  - not reliably

(IMPORTANT TO WRITE VALUE TRUE IN custom post == 'has_archive' => true, == if you need custom post type archive page

<?php
/**
* Create custom post types.
*/
add_action('init', 'create_posttype');

function create_posttype()
{
  register_post_type('testimonials',
    array(
      'supports' => array('title', 'editor'),
      'labels' => array(
        'name' => __('Testimonials'),
        'singular_name' => __('Testimonial')
      ),
      'public' => true,
      'menu_position' => 5,
      'menu_icon' => 'dashicons-format-quote',
      'rewrite' => array('slug' => 'testimonials'),
      )
  );
  register_post_type('logo',
    array(
      'supports' => array('title', 'editor'),
      'labels' => array(
        'name' => __('Logo'),
        'singular_name' => __('Logo')
      ),
      'public' => true,
      'menu_position' => 6,
      'menu_icon' => 'dashicons-images-alt2',
      'rewrite' => array('slug' => 'logo'),
      )
  );

    register_post_type('blog',
        array(
            'supports' => array(
                'title',
                'editor',
                'custom-fields',
                'revisions',
                'page-attributes',
                'thumbnail'
            ),
            'labels' => array(
                'name' => __('Blog'),
                'singular_name' => __('Blog')
            ),
            'public' => true,
            'menu_position' => 3,
            'menu_icon' => 'dashicons-book',
            'has_archive' => true,
            'rewrite' => array(
                'slug' => 'blog',
                'with_front' => false
            ),
        )
    );
}