How to Add Custom After Post Widgets in WordPress
For this part, you will need some basic CSS skills. Since the display of widgets is handled by themes, and there are so many of them, it is not possible to provide a basic style that will work for all themes. So if the after content widgets appear messed up on your site, then you need to add some CSS to fix that.
How to add a custom widget area inside a WordPress post
Next you need to position the widget area in the correct position. Think of this step as positioning it in an ordered queue – ask yourself what you want to see before and after it. You could place it before the post content or after it. You could even place it in a more normal place like the header or footer of the page. To place the widget area after the post content, but before the comments section (which is what I wanted to do with my site) you need to find and edit the correct template file. In my theme I’ve called this content-single.php.