Total Newb Question - Creating a new node with powershell

I'm looking at the "CRUD.AddNode.ps1" example, and trying to figure out how to replace

With WMI & my default Windows Credentials -
I found references to just making it ObjectSubType ="WMI";
But I'm not seeing a clear way to set the Credentials to value I would usually pick from the gui drop down?
(I'm also thinking there might be more to update, that I'm not even aware of?)

My apologies if this has been listed already somewhere and my THWACK search skills failed me.