you gotta have....

i) a Wii with internet connection
ii) SD card (2 Gb or less)
iii) SD card reader for your PC
IV) Wii game: Legend of Zelda - Twilight Princess

dont worry if you havent got the game, just borrow it - you only need it once!

When you got these you have to download some files for your SD card, but this depends on what system menu you have on your Wii.
To find this out, power on your wii then press the small 'wii' button on the bottom left hand side (Wii options) next screen, press the box on the right (with the spanner on it) and your system menu version will be on the top right hand side of the next screen.

should say something like 'ver.3.4e' or 'ver.3.3u'
Once you know what your version is post back here