How can I organize all my books on my new Nook?

I just got a new Nook. I’m looking to organize all my books/epubs on the device. I can do it on the device, but it’s clunky and very non-user friendly. I downloaded the Mac version of Nook software, but it only allows me to categorize what I’ve bought from B&N. I have about 100 books that I’d like to put on shelves and categorize. Is there anything – software – that can help? I have Mac & PC. Thanks, jellies!