How to Add Content Templates in WordPress Post Editor

How to Create a WordPress Post Template
But with custom templates for single posts and post types, you can customize the appearance and content of these different kinds of posts. This allows you to quickly and consistently add all the elements for a particular kind of post and make those different post types easier for readers to recognize and read. For example, a health and wellness website might want to have separate post types for categories like “recipes” and “workouts”—or to alert readers to featured content. Creating different templates for these different purposes can make it easier to add the appropriate content without re-creating the format every time. 
How to: Add Posts to Pages in WordPress [Tutorial]
For this “how to” – I’m going to use an example: Suppose you have a page on your website called Stories and you want to add posts under that page.  Each post will be a stand alone “story”, and the collection of all these posts will live under the page called Stories.
How to Create Re-Usable Templates for Your WordPress Blog Posts
In this post, I’m going to show you exactly how to do that using a free plugin called Simple Content Templates. I’ll start with a brief discussion of what the plugin does and, most importantly, when you should use the plugin over other options. Then, I’ll give you a step-by-step tutorial on how to use the plugin to create your very own blog templates.
How To Create a Custom Post Template
Once you’ve installed the plugin by Simon Wheatley, you’ll find a module under your post tags in your Edit Post screen. Its now time to create a post template by copying one of your existing page templates to your child themes folder.