The function of the CopyAsNewFurniture plugin has been integrated in SH3D. You don't need the plugin anymore.

It works as follows"
- select the model that you want to export
- click 3D View --> Export to OBJ format
- give a name and click Save
- select Export selection
You can then import the model again.

On the Documentation page you can download a tutorial for plugins. It also gives the locations where you can download them.

H