AWS Windows EC2 - Run Powershell Command on Instance Launch

I currently have a script (written using the PHP SDK) that starts a Windows EC2 instance when certain conditions are met.

I would like my Windows EC2 instance to automatically run a Powershell command as Administrator as soon as it is started.

How would I do this?

This is what my method looks like right now

$result = $client->runInstances(array(
    "ImageId" => "ami-43ks9as",
    "MinCount" => 1,
    "MaxCount" => 1,
    "SecurityGroupIds" => array(
        "sg-342adj8"
    ),
    "InstanceType" => "c3.medium",
    "Placement" => array(
        "AvailabilityZone" => "us-east-1a"
    ),
    "Monitoring" => array(
        "Enabled" => true
    )
));