you have to defeat team galactic in veilstone city. In their warehouse you can find the hm fly. You have to defeat gym leader maylene in veilstone city to use it. And you have to learn it to one of your Pokemon of course
Chat with our AI personalities
Teach it to a Pokemon, enter the Pokemon screen, chose the Pokemon that knows fly and select where you want to fly to.
go to the in game menu and go to Pokemon click on the Pokemon with fly and chose fly
You capture a Pokemon that has wings and find HM fly teach it to the Pokemonthat you caught and then go on to the menu and click Pokemon and thenclick the Pokemon you caught and then it says fly and just click fly.
To use fly , its at the left of where you go into Pokemon,then click the Pokemon that kknows it,and its in blue letters
Choose the Pokemon that has fly then press A on the fly choose a city or town and press A.