Instructions
Travel to Cianwood City, located west of Olivine City.
Enter the Cianwood City gym, to the west of the Pokemon Center.
Navigate up the stairs on the cliff to the west of Chuck, who is sitting in the middle of two cliffs with a waterfall pouring down on him. Use the stairs on the cliff to climb it. You must fight two Pokemon trainers; all their Pokemon are weak to Psychic-type Pokemon.
Press "A" in front of the winch at the top of the left cliff. The waterfall stops flowing.
Climb down the left cliff using the stairs.
Speak to Chuck. With the waterfall turned off, he challenges you to a Pokemon battle.