Miracast is actually a built-in feature of Windows 8.1, so there is no separate official software to "download." Think of it like a hidden bridge already built into your laptop, waiting for you to walk across it. Here is the story of how to find that bridge: The Tale of the Wireless Bridge
To download Miracast for Windows 8.1 for free, follow these steps: miracast download for windows 8.1 free
(Brilliant when it connects, frustrating when drivers go rogue.) Miracast is actually a built-in feature of Windows 8
: Your PC must have a Wi-Fi adapter and display driver that supports Miracast. miracast download for windows 8.1 free