wp_insert_post and add_post_meta

Ok so continuing partially from this thread. I’ve been able to get the thumbnail’s working. So here’s my code at the moment:

<?php
include_once"wp-config.php";
include_once"wp-load.php";
include_once"wp-includes/wp-db.php";

$my_post = array();
  $my_post['post_title'] = 'hi';
  $my_post['post_content'] = 'This is my post.';
  $my_post['post_status'] = 'publish';
  $my_post['post_author'] = 1;
  $my_post['post_excerpt'] = 'excerpt';
wp_insert_post($my_post);
echo get_the_ID();

add_post_meta(233, 'thumbnail', 'https://somedomain.com/asdadsafsdafsf.jpg');
?>

Basically the problem I have is how I can get the id that gets created in the wp_insert_post part and use in in the add_post_meta.

Any ideas?