Open a tool like Yet Another Wii Mod Manager (YAMM) or Wii Mod Lite from the Homebrew Channel. Install the WAD: Select your storage device (SD or USB). Locate the Genesis Plus GX.wad file. Select Install and press 'A'.
Genesis Plus GX is widely considered the most accurate Sega multi-system emulator for the Wii, offering 100% compatibility across several classic consoles: genesis plus gx wad