Instructions
Click the "Wii Options" button on the lower-left corner of the Wii Menu.
Choose "Data Management" on the next screen, and "Save Data" on the following one. From here you can select "Wii" or "GameCube"--if you have a GameCube memory card inserted. The procedure for editing game files is the same for titles for either Nintendo device.
Click a block to view a game file. You will be shown the name of the game, the number of memory blocks used for the save and a list of editing options.
Pick "Copy" to duplicate the file. This will only work if you have an SD card inserted, as it will copy the file from the internal memory to the card. You can also choose "Move" to transfer a game file between the card and the internal memory. Select "Erase" if you want to get rid of the file to free up space.