You could use the built in, debugging IIS (called Cassini) that comes with Visual Studio.
If you don't want to use Cassini, then the first thing you need to do is install IIS on your computer.
Also make sure to install the ASP.NET (the version that you want to target) and install the .NET frameworks that you are targeting.
Once you have done that, you will need to set up an application. This is going to vary according to the version of IIS you're using. The version of IIS is tied to the Operating System version you're using.
Once you have created the place where your application is going to run, publish your application and move the files that were published into the folder used by IIS for your application (I think you can publish directly to the folder if you are on the same machine...there's probably ways to publish across networks/the Internet as well but I haven't used it).
Then just open your browser to
http://localhost/webSite and it should work (oh wait you may have to set up a default page in for your application if you aren't using index.aspx or default.aspx)
-Frinny