Instructions
Power off your Wii.
Open the rectangular SD card cover door on the front of the system. Insert the SD card into the opening with its label facing the Wii's game disc slot. It will click into place.
Turn on your Wii and select the "Options" button at the bottom-left of the main menu. Select "Data Management" from the new window.
Select "Save Data" from the next window, and then select "Wii." Click on the "SD Card" tab at the top of the screen. The first time you select the Wii's SD card, it will ask you whether you want to format it. Select "Yes."
Transfer your saved files. Games automatically save to the Wii's internal memory, but you can free up some memory by transferring your saved files to your SD card. Select the file you want to copy from under the "Wii" tab and press "A."
Select "Copy" and then "Transfer to SD card" from the sub-menus to copy the selected file to the SD card.