Query for current post

I want to show current post.I will use this query in single template for custom post type.When click the custom post type, only the post will shown.

How can I write this query?

In wordpress developer page, $post exists as a query arg.But there is no how to use $post arg.

I write this : $post=get_post(); but it didnt work.How can I write $post as a arg in query array?