Instructions
Remove the cover for the memory expansion slot on the Nintendo 64.
Insert the N64 Game Pak into the memory expansion slot.
Replace the memory expansion slot cover.
Insert a game that supports the N64 Game Pak.
Turn on the Nintendo 64 while holding the "Start" button on the N64 controller. This will bring up the Game Pak menu.
Select the option to erase the data on the Game Pak.