Instructions
Travel to the Kanto region and head to Route 10, which is in the upper right corner of your world map. Enter the Power Plant at the end of the route and talk to everyone inside.
Exit the Power Plant and travel to Cerulean City. Inside the gym you'll find a Rocket Grunt, who you'll eventually be forced to battle outside.
Head back inside the gym and search the stacks of inner tubes in the upper left corner. You'll receive a machine part.
Take the part back to the Power Plant and speak with the director. He'll get the plant up and running again.
Head to the Pokemon Fan Club in Vermillion City. A man inside will give you a lost Pokedoll.
Travel to Saffron City where you'll find a Copycat. You can give her the lost Pokedoll in exchange for a Magnet Train Pass. You can now ride the Magnet Train from Saffron City in Kanto to Goldenrod City in Johto.