Instructions
Enable WiiConnect24 from your Nintendo Wii's "Options" menu. From the main "Options" menu, select "Internet Options," and then "WiiConnect24." Turn WiiConnect24 to "On." This will allow your system to remain connected to the Internet while the Wii is in standby mode.
Enter the 16-digit Friend Codes of the friends with whom you wish to share Miis into the "Friends" section of the Wii's main menu.
Access the "Mii Plaza" from the Wii home screen.
Select "Wii Friend" from the "Mii Plaza" menu.
Drag a Mii into the envelope and select the friend to whom you wish to send it. Your Mii will now travel to your friend's console and appear in the console's Mii Plaza.