assemblies can not turn to bundle

What I need is to include scripts in assetbundle. As I follow the guide in unity document, first turn c# scripts to assemblies. I did it with mono with UnityEngine.dll added to References. But the output .dll file can not build into assetbundle, it says Including Editor Object in Asset Bundle DefaultAsse. I don’t know which part is wrong since there is no step by step how to create assemblies in the document. gladly the .dll file can be download and scripts in it can be attach to the gameobject. So are there any way to turn dll to assetbundle? Or the right way to turn scripts to assemblies?

Problem solved, need to change .dll to .bytes. In Mac, the .dll is hidden at first, so need to make sure not just change the fiel name but change the type.

How did you turn c# scripts to assemblies and add UnityEngine.dll to References??