-There is no plugin, and no installer. It will just work when you open it. 

-To use it in another blender file, you can just copy it from 1 file and paste it in another. Or append the object. 

-the file isn't made to be exported, it can be though. Follow these steps in blender before exporting the FBX. 

-When Exporting the step that takes the longest is unwrapping the bark. You could get around this by doing tri-planar projection in the destination software for the bark only. 

-If you are confused, or have more questions feel free to ask. You can also find me on discord if you would rather talk there.