Sometimes you need to find post id. But how can you do that? Go to your admin page and go to your posts (also custom posts/ pages) page, where you can find all your posts/pages listed. Enter the desired post/page and inspect the url of that post/page, you will find something like this: http://yoursite/wp-admin/post.php?post=448&action=edit. See the number 448 – that it the post ID. Your number may differ.