How do you get a star rank in Mario kart wii in WFC?

You have to achieve a star rank or higher on each and every of the cups in each and every CC (Mushroom, Flower etc of the 50CC, 100CC etc). So, achieve a star in each one and you have a star rank. Two stars is two star rank. Three stars (very tough, shows you are a pro :) ) means you have three stars next to your name while your race.