Adding some payment instructions to WooCommerce order processing email

wc-order-email-payment-instructions.php

<?php

// Add the following to your theme's functions.php:

add_action( 'woocommerce_order_status_pending_to_processing_notification', 'watch_for_processing_email', 5 );
add_action( 'woocommerce_order_status_pending_to_on-hold_notification',    'watch_for_processing_email', 5 );

function watch_for_processing_email() {
	// only add the instructions for processing type emails
	add_action( 'woocommerce_email_before_order_table', 'add_order_email_instructions', 10, 2 );
}

function add_order_email_instructions( $order, $sent_to_admin ) {

	if ( ! $sent_to_admin ) {

		if ( 'bacs' == $order->payment_method ) {
			echo '<p><strong>Instructions:</strong> Your order will not be processed until the money is transfered</p>';
		} elseif ( 'authorize_net' == $order->payment_method ) {
			echo '<p><strong>Instructions:</strong> Please look for Acme, Inc on your next credit card statement</p>';
		}
	}
}

Many thanks.
Where should I put this please?

this gets added to your theme's functions.php

This is not working on woocommerce 2.3.7, is there a fix or a work around?

Thank you!

Could you tell me how to only add the text to the order-processing-email if chosen payment method is Paypal?

Getting the below error
Warning: Missing argument 2 for add_order_email_instructions() in /home/completecleanse/public_html/wp-content/themes/organicfood/functions.php on line 1057