Instructions
Register a friend on your console. Go to the "Wii Message Board" via a button at the bottom of the Wii Menu.
Go to "Create Message," and in the address book choose the option to register a Wii. Enter your friend's 16-digit Wii code to save him or her in your console registry.
Start the Mii Channel in the Wii Menu. Click "Wii Friend" after the Wii Plaza appears on the screen.
Press and hold the "A" and "B" buttons on the Wii remote to pick up a Mii. Place the Mii over the envelope icon at the top of the screen and release the buttons to drop him.
Choose a friend to which to send your Mii from the list that appears of your registered friends. Press "A" to confirm.