Calibre to Kobo/Paperwhite no wires?

Calibre has a server. Both the Kobo Clara HD and the Kindle Paperwhite have experimental browsers which can connect to the server. You see the library. If you then download a book you seem to be able to view it in the browser. But, it does not appear in the e-reader library. Is there some extra step required?

In short, do you have to use a usb cable to transfer books from Calibre to a Kobo Clara HD ( or a Kindle Paperwhite)? If not, then can anyone point me to a simple explanation on how to do it without hacking the e-readers?

Thanks.