Where do I go to set up my Mii to race in Mario Karts?

I've finnished the 100cc races already, but I can't find where I need to go to set my mii up to race. And no, I'm not a noob. -.-|||Essentially, you must unlock Mii Outfit A to make Miis selectable on the Character Select Screen. To unlock Mii Outfit A you must win 100cc Special Cup or play 1,650 games. There is also a Mii Outfit B which can be unlocked by completing all 32 Expert Staff Ghost Data on Time Trial Mode. I hope I helped! Good luck!