I just created this and it seems to work:
if (-not (Test-Path "C:\Program Files\WindowsPowerShell\Modules\OctopusDSC")) {
mkdir c:\temp -ErrorAction SilentlyContinue | Out-Null
$client = new-object system.Net.Webclient
$client.DownloadFile("https://github.com/OctopusDeploy/OctopusDSC/archive/master.zip","c:\temp\octopusdsc.zip")
Add-Type -AssemblyName System.IO.Compression.FileSystem
[System.IO.Compression.ZipFile]::ExtractToDirectory("c:\temp\octopusdsc.zip", "c:\temp")
cp -Recurse C:\temp\OctopusDSC-master\OctopusDSC "C:\Program Files\WindowsPowerShell\Modules\OctopusDSC"
}
I just created this and it seems to work: