Customize Single Post Template to Display Unique Sidebars

By default selecting a different Sidebar on a “per Posts” basis is not possible. The Single Post Template pulls in the same Sidebar as the Main Blog Template.
You will find the predefined Blog Sidebar in Appearance > Widgets.
If your preference is to have a different Sidebar on your Posts, please follow the steps bellow:

1 – Access your server via FTP

2 – For Karma Theme go to wp-content/themes/karma/page-layouts
– For Sterling Theme go to wp-content/themes/sterling/

3 – For Karma Theme open the Post Template file for the Layout you have chosen( blog-single-layout-left-sidebar.php or blog-single-layout-right-sidebar.php)
– For Sterling Theme open the single.php file

4 – Scroll down and locate this code near the bottom of the file:

<?php dynamic_sidebar("Blog Sidebar"); ?> 

and change to:

<?php generated_dynamic_sidebar(); ?> 

5 – Then select a Sidebar from the Sidebar selection dropdown for every Post in Post Edit.
The downside is that you will now need to manually select a Sidebar for each Post you create.

Note that you can create an unlimited number of Sidebars via Appearance > Sidebars.

IMPORTANT: In newer versions of the Themes, the Sidebar selection in Post Edit may not be available.
To fix, access your server via FTP and locate wp-content/themes/(Theme)/framework/extended/
Open multiple_sidebars.php find the following at line 61

add_meta_box(
            'truethemes_sidebar_generator',
            __( 'Custom Sidebar', 'truethemes_localize' ),
            array( &$this,'edit_form'),
            'page',
            'side',
            'low'
        );

And add the following just bellow it.

add_meta_box( 
        	'truethemes_sidebar_generator', 
        	__( 'Custom Sidebar', 'truethemes_localize' ), 
        	array( &$this,'edit_form'), 
        	'post', 
        	'side', 
        	'low' 
        	);

Now the Sidebar selection dropdown will show in Post Edit.