Please explain how I install it? I have downloaded it via the link you provided (on my Apple MacBook). What downloaded is a file called wpdm-box-com.php containing some code. I don’t know what to do with this code in order to install the add-on.
1. Please go to your WordPress admin panel.
2. go to Plugins> Add new> Upload Plugins
3. Choose the zip file you downloaded
4. Click Install now.
5. After installing activate the plugin.