Instructions
Gather up any GameCube controllers that you want to use with your Wii.
Open up the top of your Wii. If you unhook the latch on the very top of the system there should be a sort of secret compartment that holds four controller ports and two memory card slots.
Plug your GameCube controller into the ports located in the top of the Wii. If you're plugging in more than one, don't worry about attaching them in any particular order.
Load any GameCube memory cards that you would like to use into the memory card slots located next to the controller ports on top of the Wii.
Feed the GameCube game you would like to play into the disc slot on the Wii.
Enjoy the thrill of using your old GameCube controllers with your new Wii.