1) On your PC select all the music you want to copy and right click and choose 'Copy'.
2) Plug in your Nook HD+ in to your PC.
It will show up as 'My Nook' drive.
If it gives you options, choose 'Open Drive to View Files and Folders'.
If not, just open the 'My Nook' drive.
3) There will be a folder named 'My Files'. Go into that and create a Music Folder if it doesn't already exist.
4) Go inside the Music Folder - Right click and choose Paste.
5) Plug out your Nook HD+ AFTER all the files have been copied.
6) Go to the Music App. You can get a list of all music files etc. Just check the user guide for details.
7) Go to My Files section and find the music files.