It took me a while to figure this out since all of the links I could find were for older versions of Ext JS or older versions of .Net MVC. I wanted to post it here in case anyone else has problems figuring it out.
  1. Get the required Ext JS files
    • Download Ext JS, and extract the .zip file.
    • As of right now, you can get a free 30-day trial of Sencha Complete if you haven't purchased a license.
  2. Create the project in Visual Studio 2012
    • Open Visual Studio 2012 (I'm using Express 2012 for Web)
    • On the left, under "Start," choose "New Project..."
    • Under "Installed" -> "Templates" -> "Visual C#" -> "Web," select "ASP.NET MVC 4 Web Application"
    • Give the solution a name and a location.
    • Click "OK" to move to the next window.
    • For "View Engine" choose "Razor."
    • It doesn't matter if you create a unit test project.
    • Click "OK" to create the project.
  3. Add necessary files to the web project
    • Create a new folder in your web application. Call it "extjs"
    • In the Ext JS folder you extracted, find the folder called "resources". Copy the entire folder and paste it into the "extjs" folder inside your web project.
    • In the Ext JS folder you extracted, find the file called "ex-all.js". Copy that file and paste it into the "Scripts" folder inside your web project.
  4. Bundle the javascript file so your web project can use it.
    • In your web project, open the folder called "App_Start". Inside that folder, open the file called "BundleConfig.cs".
    • Inside "public static void RegisterBundles(BundleCollection bundles){}, add the following code:
      bundles.Add(new ScriptBundle("~/bundles/extjs").Include("~/Scripts/ext-all.js"));
  5. Bundle the .css file so your web project can use it.
    • In your web project, open the folder called "App_Start". Inside that folder, open the file called "BundleConfig.cs".
    • Inside "public static void RegisterBundles(BundleCollection bundles){}, add the following code:
      bundles.Add(new StyleBundle("~/Content/extjs").Include("~/extjs/resources/css/ext-all.css"));
  6. Render your bundles in the _Layout.cshtml file so that any view can use it.
    • Open "Views -> Shared -> _Layout.cshtml".
    • Add the following lines of code insice the <head></head> tag.
      • @Styles.Render("~/Content/extjs")
      • @Scripts.Render("~/bundles/extjs")
  7. Add a JavaScript reference so that you have intellisense support
    • Inside the "Scripts" folder, open the file called "_references.js".
    • Add the following code to the end of the document
      • /// <reference path="ext-all.js" />
  8. Test to be sure it's hooked up correctly.
    • Open "Views -> Home -> Index.cshtml."
    • At the very bottom of the file, type the following (notice that you should have intellisense working):
      • <script>Ext.onReady(function () { alert('hello') });</script>
    • Save your project and click the play button.
    • When the page loads, you should see an alert message that says "hello."