These examples assume you're using my Get-TenablePluginOutput PowerShell function. You can load it from the web here:
$Content = Invoke-WebRequest -Uri https://gist.githubusercontent.com/jasonadsit/db19229634c788276419c5a4134a1b7e/raw/Get-TenablePluginOutput.ps1 | Select-Object -ExpandProperty Content
. ([scriptblock]::Create($Content))
Also assumes you've already set your working directory to one with some .nessus files in it. ;-)