how on earth did u ever mod your wii in the first place if u don't know how to install wads??
Anyways, read carefully...
start ModMii, launch the ModMii wizard, tell it that your wii is not a virgin, enter in all the rest of the information truthfully. Say no to download everything except for the shopping channel, say yes to that one. Let modmii download the files and build u a guide. Follow the guide, it will spell out how to install the shopping channel wad and the IOS56 wad that ModMii would've just finished downloading. Hopefully u will learn a thing or 2 during the whole process