Homebrew Software
Save Game Extractor is homebrew software, meaning it's created by an unlicensed amateur developer. Because homebrew software is unlicensed, it does not run on the Wii through conventional means. To enable homebrew software, use a save game workaround to install the Homebrew Channel on your Wii. Note that this carries a very small risk of rendering your Wii completely inoperable. Find detailed instructions for installing the Homebrew channel at WiiBrew.org.
Installing Save Game Extractor
Once your Wii is prepared to run homebrew, you still need to install the Save Game Extractor by downloading it and its installer in zip files from WiiBrew.org. Copy the contents of the zip files into the "apps" folder on the same SD card that you installed the Homebrew Channel on. Insert the SD Card into your Wii and launch the Homebrew Channel from the Wii's main menu.
Extracting Saved Games
Save Game Extractor launches from the Homebrew Channel. The software prompts you to insert the disk for the game that you want to back up and press the "Reset" button on the front of the Wii. The program backs up the save game file for whatever disk is currently in the Wii's disk drive to the "wiisaves" directory on your SD card. If the directory does not exist, Save Game Extractor creates it. If there is already a save game file for the current game in the directory, Save Game Extractor replaces it with the new save game file.
Reinstalling Saved Games
Save Game Installer restores save game files from the "wiisaves" directory on your SD card to your Wii's hard drive. Like Save Game Extractor, Save Game Installer launches from the Homebrew Channel. Insert the disk for the game you want to restore and press the "Reset" button on your Wii. Save Game Installer then transfers the save game from your SD Card to the Wii's internal memory, overwritting the current save game on the Wii's hard drive.