If you have calibre, just turn on the wireless connection and have your Koreader connect to it.

https://github.com/koreader/koreader/wiki/calibre

Personally I'm most fond of Calibre + Calibre-Web, which masquerades as the Kobo Store and lets you use the built-in Kobo syncing mechanisms with your Calibre library instead of having to do it all within Koreader.