There are many ways to enjoy books on your Nook. One of these options is through Adobe Digital Editions. Digital Editions is a way to buy and transfer real life books onto your computer and then your e-reader. You can do this with rented library books as well. Check out this clip and learn how to transfer a DRM book to your Nook fast and easily.
The mail address on your Nook must be the same in Adobe Digital Editions otherwise this won't work.