Writing my first extension - having issues

Hi there.

I'm trying to write my first extension for AppD.  I have a Windows 2008 R2 server.  I have installed the AppD Machine Agent (4.2.7.1GA) and have created a powershell script and a monitor.xml file in the correct folder:  "./monitors/WindowsDiskUsage".

The agent log throws an error when trying to run this periodic monitor.

[Agent-Monitor-Scheduler-2] 14 Oct 2016 11:29:30,590 ERROR ExecTask - Error executing executable task java.io.IOException: Cannot run program "D:\AppTech\Utilities\AppDynamics\monitors\WindowsDiskMonitor\check_disk.ps1" (in directory "D:\AppTech\Utilities\AppDynamics\monitors\WindowsDiskMonitor"): CreateProcess error=193, %1 is not a valid Win32 application

I'm following the guidelines in the documentation:  https://docs.appdynamics.com/display/PRO42/Build+a+Monitoring+Extension+Using+Scripts#BuildaMonitoringExtensionUsingScripts-create_script

How do I inform the agent that my monitor is a script, and not a  Win32 application?

Thanks in advance!