Just took posession of a Kobo Libra and was frustrated by the lack of wireless transfer options so I do the following:
1. Start the Calibre Content Server
2. Start the Kobo Experimental Browser (If you don't have that page, type "devmodeon" into the search box and restart your Libra - you should see "beta features" in the "More" menu and the Web Browser embedded in there
3. Enter the URL for the Content Server as given in Calibre, including the port, as follows (in my case it's
http://10.0.0.xxx:abcd) where abcd is the port.
4. Do NOT hit the GO button - instead open the ellipsis menu (lower right) and hit ENTER - this will give you a "MOBILE" version of the Content Server webpage - you should see your Main Calibre library (or get a choice button if there's more than one)
5. Just tap on the type of file, e.g., epub and the Libra will offer to download.
I like this much better than messing around with FTP, clients, etc but YMMV