Automatically import content to wordpress from a json file

You can use wp_insert_post() to add a new post programmatically. For Example,

$my_post = array(
  'post_title'    => wp_strip_all_tags( $json->title ),
  'post_content'  => $json->body,
  'post_status'   => 'publish',
  'post_author'   => 1,
  'post_category' => $json->categories
);
 
// Insert the post into the database
wp_insert_post( $my_post );

Your link has expired so I could not see the structure of JSON data. But the answer would be the same. Set up a cron job or use their webhook (if they have any) to call a page where you have set up this wp_insert_post()for automatic posting.