I just started playing Mario Kart 8 and I can't figure out how to be able to use the Nunchuck for Player 1's controller. I can use the pad just fine, but I don't even see an option menu for setting which controller I want to use. Can I only use the nunchuck in multiplayer or something?
The controller used by the first player is the controller that was used to pass the title screen, before the menu where you can select "Single Player", "Multiplayer", etc. You can pass this title screen with any kind of supported controller.
If the wrong controller has been used, you can back out to the title screen with the B button and start again with the correct controller without needing to reset the game entirely.