This is the guide you should use to mod your vWii. Be sure to read it several times before trying it.
It is also strongly recommended that you don't install any wads aside from what's included in this guide. Wii U has ZERO brick protection so if you install a bad wad that bricks your vWii, you're chances of getting it working again are nearly 0%.
If I spelled something wrong, I'll just blame it on auto-correct