Get all 16 Kanto and Jhoto badges and then talk to Professor Oak. He tells you that Mt.Silver is now accessible and he will give you HM 8 which is Rock Climb. Go through Route 22 and travel up Mt. Silver. When you reach a cave, go to the East path when you have to use Rock Climb when you get there. Soon you'll reach the peak of Mt. Sliver where Red is standing. Talk to him and you will battle him. He has the highest leveled trainer of ANY pokemon game so get ready for the true battle of pokemon! Train hard and get ready for this epic fight.
Pokemon Trainer Red
One thing I recommend is to use an Electric type pokemon to battle with Blastoise, Charizard, and Lapras. Another thing, when you battle Red, there will be a Hail effect in the weather.