How to output widget

Check this out, it may guide you in the direction you need:

First:

register_sidebar( array(
    'name'          => 'Social Media button',
    'id'            => 'smb',
    'before_widget' => '<li>',
    'after_widget'  => '</li>',
) );

Second code:

public function widget( $args, $instance ) {
    $output = $args['before_widget'];

    $output .= '<a href="' . $instance['url'] . '"  class="fa fa-' . 
        $args['icon_title'] . '">' . $instance['title'] . '</a>';
    $output .= $args['after_widget'];

    echo $output; // <li><a href="https://wordpress.stackexchange.com/questions/229461/[URL]" class="fa fa-[ICON]">[TITLE]</a></li> 
}

The output from those changes will be :

<h1><li><a href="http://url.com" class="fa fa-">New title</a></li><li><h2 class="widgettitle">test1</h2>
        <div class="textwidget">test2</div>
</li></h1>

And will only do this on the social sidebar.