can't run the example of "3D Tiles.html"

I downLoad the cesium libary (https://github.com/AnalyticalGraphicsInc/cesium/tree/3d-tiles),then I put the it in IIS ,Then I run the example of
"https://github.com/AnalyticalGraphicsInc/cesium/blob/3d-tiles/Apps/Sandcastle/gallery/3D%20Tiles.html" , I Get the error in firefox debugger
error:"NetworkError: 404 Not Found - http://localhost/Cesium3DTile/cesium-3d-tiles/Source/Cesium.js"
"Error: Script error for: Cesium
http://requirejs.org/docs/errors.html#scripterror
http://localhost/Cesium3DTile/cesium-3d-tiles/ThirdParty/requirejs-2.1.20/require.js
Line 165"

what's wrong?

Hello,

Take a look at our contributor documentation for instructions on how to build and run the code: https://github.com/AnalyticalGraphicsInc/cesium/tree/master/Documentation/Contributors/BuildGuide

Best,

Hannah