you have to have a pokemon that knows surf(found in ecruteak city)surf to the whirl islands. then go left. the you're there
you use surf
its not in that game. its in HG and SS
SURF!
You have to go into the Cianwood City and after you defeat the gym leader in Cianwood someone gives it to you.
you go to olivine then battle jasmine
just go with the flow.
go to cianwood and go to the medicine building
You have to get surf, then surf to cianwood. It'll be in the cianwood pharmacy.
you go back to olivine
You go to the Pharmacy in Cianwood city. Cianwood city is on the other side of the sea, so it takes a few minutes to get there.
you go to cianwood city and go into the house to the left of the pokemon center
You need to go to Cianwood Pharmacy and get the Secretpotion.
go to cianwood pharmacy hope that helped
go to cianwood city and go to the house in the bottom middle.
Cianwood in not in Kanto, therefore, you can't in yellow.