Editing the Checkout Shipping

[kobra]

Try editing a copy of this file /includes/languages/english/checkout_shipping.php

and look for this to edit/add to

define('TEXT_CHOOSE_SHIPPING_METHOD', 'Please select the preferred shipping method to use on this order.');

Might try this

define('TEXT_CHOOSE_SHIPPING_METHOD', 'Please select the preferred shipping method to use on this order.</br>Note: Shipping takes 5-7 days.');