wooattributes-acf.php

<?php

class ACF_Product_Options {

	static $slug = 'hwid_attributes';

	public static function init() {

//		Gather the global attribute types
		$attribute_terms = wc_get_attribute_taxonomy_names();

//		Initialize the array for holding the location rules
		$group_filter = array();

//		Loop through the attribute types and build our field group location rules: IF this OR this OR this
		foreach( $attribute_terms as $attribute_term ) {
			$group_filter[] = array( array(
				'param'    => 'taxonomy',
				'operator' => '==',
				'value'    => $attribute_term,
				'order_no' => 0,
				'group_no' => 0,
			) );
		}

		if ( function_exists( 'acf_add_local_field_group' ) ) {
			acf_add_local_field_group( array(
				'key'         => self::$slug,
				'title'      => __( 'Product Options', 'custom-site' ),
				'fields'     => array(
					array (
						'key' => self::$slug . 'imagestab',
						'label' => __( 'Images', 'custom-site' ),
						'type' => 'tab',
					),
					array (
						'key' => self::$slug . 'detail',
						'label' => __( 'Detail Image', 'custom-site' ),
						'name' => 'detail_image',
						'type' => 'image',
						'instructions' => 'This image should have a transparent background.',
						'return_format' => 'array',
						'preview_size' => 'thumbnail',
						'library' => 'images',
					),
				),
//              Use the custom location rules to target all global attribute Edit pages
				'location'   => $group_filter,
				'options'    => array(
					'position'       => 'normal',
					'layout'         => 'default',
					'hide_on_screen' => array(),
				),
				'menu_order' => 0,
			) );
		}

	}
}

Hey Mate! I copy pasted this code in functions.php file and it didn't do anything.