Open the Unlock DLC.dlc file using JDownloader.

If the file is actually a extension (or a zip containing one) used to download content via a container format ReviverSoft :

Right-click Unlock DLC.zip and select "Extract All" or use a tool like 7-Zip/WinRAR to extract the contents to a folder.

Download and install JDownloader , a Java-based download manager designed to handle container files.

JDownloader will decrypt the file and add the download links to the link grabber list.