Well you'll need the Homebrew Channel, and then I think you'll need a program called Ocarina.
You'll have to Google search for where to download them and how to install them. But if you updated to the latest system menu (4.2) released a few days ago you won't be able to use either of those until the homebrew team find a way around it.
Also, if you are caught cheating Nintendo will ban your console to prevent you from playing online.
http://hackmii.com