Instructions
Insert your "Super Mario 64" game cart into the Gameshark device. Insert the Gameshark device into the game port on your Nintendo 64.
Turn your Nintendo 64 on to access the Gameshark's main menu. Select the "Start Game" option in the main menu, and make sure the code generator option is set to "On." Then select one of the "Start Game" options in the menu to begin playing.
Press the "Gameshark" button on your Gameshark device while playing to open the Gameshark menu.
Select the "Code Generator" option in the main menu, then select either the "Known Value Search" or "Unknown Value Search" option. The Code Generator will perform a search through the game's memory for various items that can be manipulated.
Change the line of code that appears in the code search to suit your liking. For example, if you find a line of code that ends in "05," this could reference the number of lives for your character. Change the "05" to "99," then press the "Start" button to view the possible effects of the code. In this example, your character should now have 99 lives.