Instructions
Travel the Kanto region, completing objectives and battling the wild pokemon found in the tall grass who automatically attack the main character. Use your strongest pokemon to attack the wild creatures and use pokeballs if you want to capture the pokemon when they are weak.
Review the pokedex every time you find a new type of pokemon you have yet to battle. The pokedex automatically updates to include new information about discovered pokemon.
Obtain the information pertaining to 40 different types of pokemon. Search the tall grass in every area that you travel to as you complete the main storyline of "Pokemon LeafGreen" to discover new pokemon because every area has unique pokemon.
Return to Professor Oak's house in Pallet Town and go to the upstairs observation room in the gatehouse that connects to Celadon City and Cycling Road. Press "A" to speak to the aide located in the room, who gives you the amulet coin if you have 40 pokemon listed in your pokedex. If you don't have 40 different pokemon, he will not give you the coin.