After my lengthy complaints about the file/preset organisation here is the answer:
In your "Documents" folder there should be a Native Instruments folder, in which there is a Reaktor folder, there are two folders, ensembles and library.
Use the "Ensembles" folder.
It's best to drag and drop the stuff from there, or to navigate Reaktor there.
(as i wrote, if you like the ensemble, save it additionally as Logic setting, that's the best way to find things again.)