How to add fields to Blog Page/index.php by Carbon Fields

I am trying to add fields to Blog Page/index.php by Carbon Fields but its not working

carbon.php

Container::make( 'post_meta', __( 'Blog Page Settings','carbon' ) )
        ->where( 'post_template', '=', 'index.php' )

        ->add_tab( __( 'Page Header Section','carbon' ), array(
            Field::make( 'text', 'blog_page_header_title', __( 'Title','carbon' ) )->set_width( 100 ),
            Field::make( 'text', 'blog_page_header_sub_title', __( 'Sub Title','carbon' ) )->set_width( 100 ),
        ) );

index.php

<h4><?php echo esc_html(carbon_get_the_post_meta('blog_page_header_title')); ?></h4>
<h1><?php echo esc_html(carbon_get_the_post_meta('blog_page_header_sub_title')); ?></h1>