How do you put your Mii on the dance floor in dance dance revolution hottest party 2

You have to do groove arena, it is the first option on the main menu.
Then you do however many players there are.
You then, if you haven't done it, beat the first section.
You then move on to the second section and use the pad to change to a section called something like arena go-go.
You must fill all the requirements for this arena.
You then get the mii character.
To use: Go to the character selections, there will be a new one labeled mii. Pick this option.
You will then be able to choose from Wii or guest. Your choice.
Pick the mii you want from that menu.
You will get some options for clothing, for boys or girls. Press - or + to change the clothing of that style.
Enjoy.