How do you get waterfall instanly on Pokemon Gold?

You can't get Waterfall instantly in Pokémon Gold. It requires you to reach a certain point in the game and learn it from a specific trainer. Here's how to get it:

1. Beat the Elite Four and become the Champion. This is the main requirement to unlock access to the move.

2. Travel to the Whirl Islands. This is a new area accessible only after becoming Champion.

3. Find the Move Tutor. This trainer is located on the northernmost island, near the entrance to the Ruins of Alph.

4. Speak to the Move Tutor. He will offer to teach you the HM for Waterfall, which you can then use to access new areas and progress further in the game.

Remember: You need to have a Pokémon that can learn Waterfall, such as Squirtle, Totodile, or Poliwhirl, before you can use this HM.