如何添加未包含在WooCommerce产品中的虚拟产品的购物车？

I have almost the same issue with this question Adding a product to cart with custom info and price but the thing is that I want to pull the data from a custom products which is from a custom post type.

Well I added the code from the above question and don't know what to do next. LOL I'm confused.

Also I tried this code to add a product:

   $product_ids = '6547';
   $add_to_cart_url = esc_url_raw( 
       add_query_arg( 'add-to-cart', $product_ids, wc_get_checkout_url() 
   ) );

It's working fine when the id is from the woocommerce product but when I tried to insert a non product item which is a hard coded id it will not show in my cart.

So basically I just want to add a order set of custom product from my custom post type data and use the cart and checkout feature of woocommerce.

Is that possible? How can I do it?