It's the same process either way. On the Wii you can use Banner Bomb, but on the Wii U you can just a save file exploit. Just copy the save file from SD to the Wii (U), run the game and follow the instructions to trigger the exploit, while you have the hackMii installer on your SD (not SDHC) card (otherwise you will only crash the console) and install HBC from there. After that you just add the homebrew to the /apps/ directory (that you will need to create) on your SD card and load from HBC in the Wii Menu.