Extract the archive to a folder on your desktop. Inside, you will likely find .ico files or a .dll library file.
Here is a proper write-up regarding the . Windows 7 Icon Pack By 2013 Windows 8.1
Whether you are running a legacy machine for retro gaming or just miss the distinctive look of 2013, this icon pack is a great way to revitalize your desktop. Extract the archive to a folder on your desktop