If you are looking to play the game on a modded Wii, you generally use an file through a loader like USB Loader GX
A "forwarder" WAD adds a shortcut to your Wii menu that launches the game from your SD card or USB drive without needing the Homebrew Channel every time. new super mario bros wii wad file download link
Digital backups ensure you can play the game even if your original disc becomes scratched or the Wii disc drive fails. How to Get New Super Mario Bros. Wii Files Safely If you are looking to play the game