Select Nintendo eShop on the HOME Menu to launch the Nintendo eShop.
Select the account you want to use.
Select Enter Code on the left side of the screen.
Enter the 16-character download code.
Some retailer cards for Nintendo Switch software will include both a Control Number and a Download Code. Make sure that you are entering the Download Code (usually begins with a B, no hyphens in the number) and not the Control Number (usually begins with an S, has hyphens).
Any letters and symbols not used with prepaid codes (i.e. O, I, Z, commas, hyphens, etc.) will be disabled from the on-screen keyboard.
Select OK to confirm. The game will begin downloading once the code is confirmed.
The game icon will appear on the HOME menu, with a download status bar. The status bar will disappear once the game download is complete.