Instructions
Insert the Rumble Pak into the slot on the back of your N64 controller.
Begin playing the game and walk to the fishing hole in Lake Hyila. If you are adult Link, go to the Temple of Time and become young Link before walking to the fishing hole.
Talk to the Fishing Man at the fishin pond. Give him 20 rupees, and he will give you the fishing rod in exchange. Since you have the Rumble Pak installed, the fishing pole automatically becomes a Rumble Pak fishing pole.