You'd probably have better luck posting this in the ODP.NET forum, as this one is for .net stored procedures that reside inside the database.
To answer your question though, there's no Oracle specific documentation regarding PowerShell as there's nothing Oracle specific about it. However you'd go about executing any external .NET library should apply to using ODP.NET as well. However, if you have access to My Oracle Support, the following note may help you out with a simple example:
Using ODP.NET in Combination With Microsoft Powershell to Retrieve Data (Doc ID 848177.1)
Regarding general "executing DML/DDL statements from ODP.NET", if you need assistance with that, the following walkthrough should get you started: