Axtlar has the right instructions (if you still haven't gotten your Wiimotes working).
Simply, turn on the Wii, then press the "sync" button on the Wii and Wiimote. Takes a couple seconds, then registers the Wiimote. I just got my second Wiimote yesterday, and just put batteries in and hit the sync buttons and boom, my 2nd mote works.
Good luck with yours.