Instructions
Power on your Wii and click "Start." Click the "Wii Shop Channel" from the Wii Homepage.
Agree to the user terms if it's your first time on the channel. Next click, "Welcome to Wii Shop Channel," followed by, "Start Shopping."
Click the button that reads "Add Wii Points." Followed by "Redeem Nintendo Points Card." You must scratch the silver line off the back of the card to reveal your Wii Points code.
Enter the code on the screen with the Wii remote. Click "OK," then "Redeem." Wait for the order to process and you can begin shopping with your Wii Points.