I havn't played in awhile, so I don't remember the towns name, but when you go look for the medicine for the pokemon in the lighthouse, you have to go to Cinawood Island or something like that. Once you beat the gym leader of the town, walk outside and talk to his wife. She's pacing side to side just below the gym entrance. She'll give you HM02 and say her husband was getting chubby.
Chuck's Wife (in front of the gym) Will give you Fly after you beat Chuck
You Use fly and just fly there
Assuming you mean the hm fly on Pokemon crystal, you get it from the lady out side of Cindawood gym.
Outside Cianwood City Gym.
It depends on the Pokemon game version. It is different every version.
Talk to the woman outside the Cianwood City Gym.
Driftveil City.
liquid crystal isn't actually a real Pokemon game
In Pokemon Liquid Crystal, HM Fly is given to you by an Aide in the Goldenrod City Department Store after you have received the Glacier Badge. You can then teach the HM Fly to one of your Pokemon to fly to different locations in the game.
Go fly
You can use fly anytime you are outside.
You get it from a girl in Cianwood after you beat chuck.