Hi,
When you create/edit a product, in the Files area, you can use the "+" button:
www.hikashop.com/support/documentation/i...uct-form.html#images
When you click on that button, it will open a popup. There, select "Specify file location" and in the "file path" setting, enter the URL of your hidden youtube video.
Once the product is purchased, the user will receive a download link from your website, and when clicking on it, the user will go through your website before being redirected to the hidden youtube video page.