Welcome, Sunshine!
Are your Kobo books on your computer? If so, you should be able to plug your Nook into your computer (via USB cable, I'm guessing), then find the books on your computer and transfer them to the Nook. "Drag and drop" means to hold the left mouse button down, grabbing the file you want to transfer, then move your cursor (with the file attached to it) to the location where you want it to go and let go of the left mouse button. The file then drops into its new place.
If your computer sees your Nook as a drive this will work, or if you are moving books from Adobe Digital Editions. I don't know what the Nook and Kobo interfaces (on your computer) look like so I can't help you much more.
Good luck!
If you need more help, you might want to ask in the Nook forum.
I'll bet you're not the first to make that transfer!!
Enjoy your new ereader!
