The readme file for the PowerShell Modular Input AddOn says docs are at https://docs.splunk.com/Documentation/AddOns. This link is dead
I've been to http://docs.splunk.com/Documentation/AddOns/latest/MSPowerShell/Description and don't see an entry for the PowerShell Modular Input AddOn
Where are the docs for the PowerShell Modular Input AddOn?
Try this article, it has some really good details: