How can i play as my mii in mario kart?

To play as your mii in Mario Kart Wii you have to win the 100 special cup. You will then unlock your mii and they will be in a racing suit that matches the color of the shirt you choose. For example my mii has a purple shirt so her racing suit is purple. You can also unlock mii outfit b (boys were mario clothes/girls wear a shorter version of peachs dress) by unlocking 32 expert staff ghosts in time trials