How do you get the hidden move flash?

To obtain the hidden move Flash in Pokémon games, you typically need to find and defeat a specific Pokémon known as a gym leader or complete a certain task. In most games, Flash is taught by a character or found in a specific location, usually within caves or dark areas. Make sure you have a Pokémon that can learn the move, then teach it Flash from your bag or Pokémon menu. Remember that Flash is often not required to complete the game but can help illuminate dark areas.