Add custom widget to anywhere you want

Register widget in functions.php

 
// =========================================================================
// REGISTER NEW WIDGET
// =========================================================================
function custom_widgets_init() {

    register_sidebar( array(
            'name' => 'Custom Widget',
            'id' => 'custom-widget-id',
            'before_widget' => '<div class="custom-widget">',
            'after_widget' => '</div>',
            'before_title' => '<h4 class="custom-title">',
            'after_title' => '</h4>',
        ) );

}
add_action( 'widgets_init', 'custom_widgets_init' ); 

Place this code where you want to appear the widget

<?php dynamic_sidebar('Custom Widget'); ?>