Details about integrating Unity into windows application

I found a brief page about how to integrate unity into windows application: Unity - Manual: Integrating Unity into Windows applications

The page tells us that we can load UnityPlayer.dll to start Unity inside our own process, but I need more details.

Is there anyone who figured it out?
It will be so appreciated that a sample project should be provided.

I Found someone’s post:
https://forum.unity.com/threads/passing-parenthwnd-to-unitymain-function.517656/