Enter the 16-digit code listed on the Receipt into the Wii U Nintendo eShop, and the download for the DLC will begin. Once finished, the purchased DLC will be available on Super Smash Bros. for Wii U.
In Super Smash Bros. for Wii U you can select the Notices & eShop button to access Nintendo eShop, where you can purchase the add-on content. You can increase the number of playable fighters and Mii ...