Do I need to register a new eReader in order to transfer ebooks?

I recently got a new Nook, and now when I connect it to my computer (Windows 😎 it doesn't show up in Adobe Digital Editions for me to be able to transfer ebooks. I did manage to get them on my nook by copying and pasting through the documents folder of my computer, but when I try to open them it say Error Dialog: User not found.