Creating a widget to open mini-cart - php

Question

I have a plugin which adds a mini cart to my website so when I add a product to the basket the mini cart pops out from the page.
The whole plugin works great. The only thing I want to do is create a widget to put in the header area of the website to open the mini cart, just like the hovering basket does in the bottom right hand corner of the page.
The code that it says to use is:
public_woo_amc_show()
The problem is, that I'm totally unsure, how to add a custom widget. I've googled and managed to code this code:
// Register and load the widget
function wpb_load_widget() {
register_widget( 'wpb_widget' );
}
add_action( 'widgets_init', 'wpb_load_widget' );
// Creating the widget
class wpb_widget extends WP_Widget {
function __construct() {
parent::__construct(
// Base ID of your widget
'wpb_widget',
// Widget name will appear in UI
__( 'WPBeginner Widget', 'wpb_widget_domain' ),
// Widget description
array( 'description' => __( 'Sample widget based on WPBeginner Tutorial', 'wpb_widget_domain' ), )
);
}
// Creating widget front-end
public function widget( $args, $instance ) {
$title = apply_filters( 'widget_title', $instance['title'] );
// before and after widget arguments are defined by themes
echo $args['before_widget'];
if ( ! empty( $title ) ) {
echo $args['before_title'] . $title . $args['after_title'];
}
// This is where you run the code and display the output
echo __( 'Hello, World!', 'wpb_widget_domain' );
echo $args['after_widget'];
}
// Widget Backend
public function form( $instance ) {
if ( isset( $instance['title'] ) ) {
$title = $instance['title'];
} else {
$title = __( 'New title', 'wpb_widget_domain' );
}
// Widget admin form
?>
<p>
<label for="<?php echo $this->get_field_id( 'title' ); ?>"><?php _e( 'Title:' ); ?></label>
<input class="widefat" id="<?php echo $this->get_field_id( 'title' ); ?>"
name="<?php echo $this->get_field_name( 'title' ); ?>" type="text"
value="<?php echo esc_attr( $title ); ?>"/>
</p>
<?php
}
// Updating widget replacing old instances with new
public function update( $new_instance, $old_instance ) {
$instance = array();
$instance['title'] = ( ! empty( $new_instance['title'] ) ) ? strip_tags( $new_instance['title'] ) : '';
return $instance;
}
} // Class wpb_widget ends here
All I want is an icon that I can click and it pops the mini-cart out exactly how it does on the website above already.
I've tried adding this code where I thought it would go within this widget but I'm no expert and am definitely limited with JavaScript.