I know that you give the wrapped presents to "carolers". However, are carolers NPCs, or users? And if they are users, how would one carol? This is my first event, and I'm a little confused. Thank you!

Carolers are other users! To carol, click on this button (located near the top of the page, next to your avatar), and it will take you to the festival overview page. Then click the "holiday caroling" link. It will take you to your caroling page, where you can answer the carolers at your door. You can also click the green arrows in the info box to visit other users. :)
I hope you enjoy your first festival! ^^

Oh, thank you very much!! ^u^