You can get the HM Flash by going to the Goldenrod city and heading to the fifth floor in the main department store. Speak to the woman in the store and purchase Flash, however the version is a TM 70, not HM. You can also get it for free at the Sprout Tower in Violet City.
You can also obtain other moves throughout the 'Pokemon HeartGold' game on DS. One popular move is HM Surf, also known as HM03 which allows water-based Pokemons to surf across water which can open access to new areas. To get this move you need to head to Ecruteak City and walk to the centre of town and access the theatre. When you get in there you'll see a character hassling one of the dancers. This is Team Galactic Grunt and when you approach him you'll be requested to battle each other. Once you've defeated him you'll get intercepted by an old man while leaving the theatre and he'll give you the HM Surf move.
The Rock Smash move or HM 06 is another popular move that you can obtain during the game. It allows you to clear boulders that are obstructing your way. In order to get this move you need to travel to Violet City and walk into the 'Violet Gym'. Here you will have to battle the gym leader called Falkner, who uses a flying-type Pokemon. If you defeat Falkner then you will be able to travel to the gatehouse in Violet City which is in the north-west region. Once you get there speak to the man next to the giant Pokemon tree and he'll give you the Rock Smash move.
You can also obtain other moves throughout the 'Pokemon HeartGold' game on DS. One popular move is HM Surf, also known as HM03 which allows water-based Pokemons to surf across water which can open access to new areas. To get this move you need to head to Ecruteak City and walk to the centre of town and access the theatre. When you get in there you'll see a character hassling one of the dancers. This is Team Galactic Grunt and when you approach him you'll be requested to battle each other. Once you've defeated him you'll get intercepted by an old man while leaving the theatre and he'll give you the HM Surf move.
The Rock Smash move or HM 06 is another popular move that you can obtain during the game. It allows you to clear boulders that are obstructing your way. In order to get this move you need to travel to Violet City and walk into the 'Violet Gym'. Here you will have to battle the gym leader called Falkner, who uses a flying-type Pokemon. If you defeat Falkner then you will be able to travel to the gatehouse in Violet City which is in the north-west region. Once you get there speak to the man next to the giant Pokemon tree and he'll give you the Rock Smash move.
