Setting up an Android project is really simple. The document you linked is outdated and you don’t need to move any files at all.
Unity
- Goto
File -> Build Settings -> Android
and clickSwitch Platform
- Enable
Google Android Project
- Click
Export
and choose where you want the Android project to be
Android Studio
- Import or open the project you have just created with Unity
- Done 🙂
If you want to display the Unity engine inside a subactivity, I suggest you take a look at this answer.
If you’re completely unfamiliar with Android development, you should start with a simple “Hello World” app without complicating things by adding Unity to the mix. Just follow some of the official Android guides.