Tech help

I got David a Blackberry Playbook since they were massively reduced. Now we're trying to put some books on it using Calibre. There's a new Blackberry plug-in on Calibre and I got it to recognize the PB and transfer a book over to the 'books' folder (not the installed Kobo folder) but we can't find it.

I'm stabbing at the screen trying to open things and getting nowhere.

Anyone have a PB who knows how to get books onto it and where they are when you do?

TIA!