Highlight a file at the saved game selection screen (make sure to keep the file highlighted while inputting the code). First, hold Nunchuk C and press 1 three times, then release the button. Now hold Z and press 1 four times, then release the button. Finally, hold C + Z and press 1 five times. All four gems will appear to confirm you've correctly inputted the code. Select that saved game file and enter the sport selection screen to see that everything is now gold.