Thank you for your question. Using Content Editor plugin you can edit all post types specially Posts. But if you want to edit the layout of Post page e.g. remove sidebar or add one more widget area, then you should refer to your theme documentation. Usually you need to create single-post.php file and create the layout of the Post in a way you need. You can refer to structure of some page templates provided in your theme or single.php file – customizing it.