Make a GCT of your code. (go here for a tutorial.)
Make a folder called "codes" on the root of your SD card. Paste your GCT into the folder, make sure its named correctly. (America = RMCE01, European = RMCP01, Japanese = RMCJ01, Korean = RMCK01)
Download the riivolution patch, unzip it and put the files inside of the riivolution folder on your SD card (You need riivolution downloaded, to download it, click this link and put the contents of the zip into your apps folder.)
Open riivolution and set OCARINA_CODES to Enabled and OCARINA HANDLER to GXDRAW HOOK, then press launch
Some file directories may be different on Wii U compared to Wii. This tutorial was based with Wii in mind.
Download the NinjaWFC Code.
Right click your iso/wbfs in Dolphin Emulator, click properties, then go to the Gecko Codes Tab.
Click "Add Code", Add a title for the code, and paste the code into the text box. Simply launch the game and it should work!