Use multi mod manager to install the wad.
First place the wad file in the wad folder in your SD card.
Then in multi mod manager, choose wad manager. Then choose the wad you're installing and select it. Now install it an you're done.
Get MMM from here: Download Multi-Mod-Manager 13.4 » Wii Homebrew Applications - FileTrip
Choose manual download, not automatic.
Caution: Installing a bad wad, or a VC game from another region can be dangerous, can result in a brick. A banner brick I believe it's called.