I’m assuming that you’re asking how to do it with code? (Doing it in backend is pretty easy – just try to edit parent page and see the ID in URL).
So how to check post parent in code? It’s also very easy – direct parent is stored in post_parent
property. If post has no parent, it will be 0
.
So all you have to do is:
global $post;
$direct_parent = $post->post_parent;