Things You'll Need
Instructions
Find the 12-digit friend code for your Wii. (Note: this is not your Wii's code, which is a 16-digit number.) You can find your Mario Kart Friend Number by going to the Mario Kart Channel and choosing the "Friends" option. Your Mii will be at the bottom center of the page and your 12-digit number will be below it.
Find your region information on the Mario Kart Channel under the "Region" option.
Exchange your code with friends to play against them online. If none of your friends have Mario Kart Wii, you can connect to people who do on a website where people exchange friend codes. Doing an internet search for "Mario Kart Wii Friend Code" will bring up several sites on which people exchange codes.
Use the code to add the person to your friends list (also found in the Mario Kart Channel) and you'll be able to race against them online.