you cant. you have to go to fuchsia city and surf wouth then west and you will get to seafoam islands. That's not true, ju can just surf to the right and you'll get to seafoam island.
You go west from Cinnabar Island, you enter (there should be a picnicker to the right and a sign to the left). Do not go down the ice stairs! That is where you get Articuno once you beat the game in...