I couldn't find this described in the documentation either, how to use it yes, but not how to transfer it to the IPAD. Maybe Tim could provide us a direct link?
Anyway, I solved it by using i-FunBox (
http://www.i-funbox.com/), a free software for managing your ipad. You can transfer the files you need from the Custom data folder on you pc to the same folder on the ipad. Works well on mine.