Instructions
Plug two controllers into the Nintendo Entertainment System. The controller ports are on the front side of the console.
Insert the "Super Mario Bros." cartridge into the NES console.
Press the power button on the front of the console and wait for the game to load to the main menu. Press "A" on "Super Mario Bros." if you have the "Super Mario Bros./Duck Hunt" cartridge.
Press "Select" on the first controller to highlight the "2 Player Game."
Press "A" to start a new game with two players.
Press "Right" on the first controller and run directly into the first Goomba, defeating Mario. Only when an enemy defeats Mario can Luigi get a turn.
Play the game as normal using the second controller to play as Luigi. If an enemy defeats Luigi, it will be Mario's turn again.