Instructions
Insert your Wii SD card into a compatible slot reader on your computer.
Download the official Ftpii application from WiiBrew. WiiBrew hosts the most up-to-date version of the application and provides release news about each update.
Transfer the downloaded folder to the "Apps" folder on the SD card. The default name is "FTPii." If you want to add a password to the application so no one can access the network, right-click on the folder and select "Rename." Change the folder name to "FTPii_ADDPASSWORDHERE." Replace the "ADDPASSWORDHERE" with a password and keep the underscore in the folder title.
Remove the SD card from the computer and insert it into the Wii. Select the Wii "Homebrew Channel" with the Wii remote and press "Start."
Select the "FTPii" application from the list. Point and press "A" on "Run." The screen turns black for a few moments and then a password prompt appears, if you created one.
Write down the information that appears on the screen. There will be an IP address listed and then a Port. Use those with the FTP application that you own to emulate the network connection and access your Wii SD card.