After purchasing the External Images Plugin, you will receive a zipped file, from there, please follow these steps:
In your WP admin area, click on “Plugins” -> Add new -> Upload Plugin -> Choose file. From there you can select the zipped file you selected and install the Plugin. Once install, click the Activate button.
Activating this plugin forces WordPress to read images from either the external_image_url custom meta field. This field can contain one or many image URLs for images stored anywhere – they can be CDN images from affiliate networks, or your own images stored on Amazon S3 – it doesn’t matter.
To set an external URL, edit any of your posts or products and find the ‘External Images’ section. You will find a field that you can populate. Once you populate it with the URL of an image and save the product/post, then that image will be used as the featured image.
You can also fill this field with multiple images, separated by commas, and then the first image will be the featured image and the others will be placed in a gallery on the single post/single product pages.
If you need to import images, you should import them to the custom meta field external_image_url. If you import multiple images, separate them by commas.
SSL & HTTPS considerations
If you have a site using https and you provide an image url which is only http, the External Images plugin will test if it’s possible to load that image using https to avoid breaking the SSL padlock.
If it is possible, External Images remembers this fact for that image domain, and will always switch images over to https in future for that domain.
If it is not possible, External Images remembers this too and will proxy all these http images through your own server – that means it temporarily downloads the image to your server then displays it to the user, so to the user it looks like it came from your site.
External Images alters your meta tags so that sites like Twitter, Facebook, Google etc will pull the preview image from your external featured image.