You configure the action type in the web config.xml.
Code:
<rule name="Imported Rule 1" stopProcessing="true">
<match url="^(.*)$" ignoreCase="false" />
<conditions>
<add input="{HTTP_HOST}" pattern="^example\.com$" />
</conditions>
<action type="Redirect" redirectType="Permanent" url="http://www.example.com/{R:1}" />
</rule>
Is what I am told on this page:
http://www.iis.net/learn/application...-iis-webconfig