Instructions
Beat the game on Normal or Hard difficulty. There are seven levels to complete, most of which will take you slightly under an hour to complete. After the game's credits, you will be placed back in the "Main Menu."
Press the "A" button on "Mission Select."
Press the "A" button on Liberty Island, which is the last mission listed, to begin playing the bonus mission. Unlike the other missions in the game, it takes place in broad daylight and allows you to further explore the land you have been fighting for.