Instructions
Turn on the Wii.
Open the SD card cover on the front of the Wii and press the "Sync" button. The sync light will begin flashing.
Remove the battery cover on the back of the second Wii Remote. Press the "Sync" button. After a second, the lights on both the Wii Remote and the Wii console will stabilize, indicating a successful sync. If you're using one, attach a Classic Controller to the expansion port underneath the Wii Remote.
Insert the "Mario Kart Wii" disc if it isn't already. Select the "Mario Kart Wii" icon on the Wii Channel Menu to start the game.
Select "Multiplayer" from the "Mario Kart Wii" main menu. Select "Two Players." Press the "A" button to sign in with the controllers you want to use. Select a track and play the game as you would during single player.