Update README.md to explain how to use .unityPackage with Free version of Unity

Author: speps

README.md

@@ -32,10 +32,16 @@ Some examples are available in this repository :
 
 ![Unity](https://raw.github.com/speps/XInputDotNet/master/XInputUnity/Screenshot.jpg)
 
-* Download the latest XInputDotNet.unityPackage from the [releases tab](https://github.com/speps/XInputDotNet/releases)
+* Download the latest `XInputDotNet.unityPackage` from the [releases tab](https://github.com/speps/XInputDotNet/releases)
 * Open the menu Assets > Import Package > Custom Package and select the package you just downloaded
 * See XInputTestCS.cs for a basic usage example
 
+#### <a name="free"></a>Special instructions for Free version of Unity
+
+* Import the .unityPackage as described above
+* Copy `[Project Folder]\Assets\Plugins\x86\XInputInterface.dll` to `[Project Folder]\XInputInterface.dll`
+* **Making a Build does NOT require to copy `XInputInterface.dll` in the same folder the your game .exe file**
+
 ### Notes
 
 * Under Windows XP, you'll need special drivers for your Xbox 360 Controller. You can find them at this address : [XBox 360 Controller for Windows Software](http://www.microsoft.com/en-us/download/details.aspx?id=34001)