This is a little harder then just add the site.

First add a site and browse to folder

Add security Anononymous.Authentication to Enables

Right click on site and Edit Permission-> Select Security and Edit

Add IUSR user to be able to use the anonymous or got to that end Edit to change user

Add IIS APPPOOL\YourSiteName and set the rights

Look in this form more

<?xml version="1.0" encoding="UTF-8"?>
<configuration>
  <system.webServer>
    <staticContent>
      <mimeMap fileExtension=".nupkg" mimeType="application/zip" />
      <mimeMap fileExtension="." mimeType="text/plain" />
    </staticContent>
  </system.webServer>
</configuration>

If you need to be able to serve other than normal files, you can add the above Web.config file in the folder used for files. Example taken from here.