If you purchase the plugin from the Elegantthemes Marketplace, you must follow these instructions:
Download
After purchase, download the .zip file from your Elegant Themes account.
Installation
Installing this plugin is as straightforward as installing any other WordPress plugin. From your WordPress Dashboard, go to Appearance>Plugins>Add New and click on Upload Plugin. Locate the .zip file on your computer and click Install Now.
Activate the Plugin Using the Divi Theme License
Please go to the Dashboard > Divi > Theme Options > Updates – there you can activate the Divi Theme license.
You do not need a separate license key for any of the third-party plugins. You need to do is just activate the Divi Theme license, that would be enough for updating – from then on, you will get an update notification.