You MUST install AIR SDK before using this extension.
Not runtime.
Download Latest Milestone: Flex 3 SDK Beta 2 or Recent Nightly Builds of the Flex 3 SDK from Adobe Labs
Flex 3 Software Development Kit
http://labs.adobe.com/technologies/flex/sdk/flex3sdk.html
On the files panel,
When the path of ADF file is defined in meta-date.
You can run HTML-based AIR applications using the ADF file that defined in meta-date.
<meta name="adf" content="application.xml">
You should set the path of adl.exe on your environment.
(As default, "file:///C|AIRSDK/bin/adl.exe")