Download the helper file
You must download and host a helper file (helper.html) on your website.
The helper file communicates with your website to resize the iframe or lightbox with the content being shown.
You must host the helper.html file in the same domain as the webpage in which you are integrating the iframe or lightbox.
You can download a copy of the helper file from the Worldpay embedded integration wizard. The wizard is available at https://payments.worldpay.com/resources/hpp/integrations/embedded/doc.