1.) Have a wii + mario kart wii disc

2.) Have it homebrewed (https://wii.guide/)

3.) Download the riivolution files from resources

4.) Drag them on to the top of your SD card

5.) Put your SD card back in your wii

6.) Boot up riivolution from the homebrew menu, make sure mkf is enabled and save to SD is off along with an other riivolution files you have and hit launch.

Now the game should launch!