CODE EXAMPLE FOR PHP

register and display wordpress sidebar

//in functions.php
function wpdocs_theme_slug_widgets_init()
{
    register_sidebar(array(
        'name'          => 'Main Sidebar',
        'id'            => 'sidebar-1',
        'description'   => 'Widgets in this area will be shown on all posts and pages.',
        'before_widget' => '<li id="%1$s" class="widget %2$s">',
        'after_widget'  => '</li>',
        'before_title'  => '<h2 class="widgettitle">',
        'after_title'   => '</h2>',
    ));
}
add_action('widgets_init', 'wpdocs_theme_slug_widgets_init');

//got to appearance->widgets and add widgets

//in sidebar.php
<?php if (!is_active_sidebar('sidebar-1')) {
    return;
}
?>

<div class="col-md-3 widget-area" id="secondary" role="complementary">

    <?php dynamic_sidebar('sidebar-1'); ?>

</div><!-- #secondary -->