u go up that one tall building in olivine city
Surf to Cianwood city and go to the Cianwood City Pharmacy. Talk to the guy in there and he will give you the medicine.
go up the stairs until you get to the top then talk to jasmine
u talk to jasmine where ever she is and battle her (WIN) and get her number same goes to Heartgold
She's still in her gym.
go to cianwood city then get it from a man
Wednesday from 10 to 19:59
building near Pokemon center on cinnabar island
there will be a secret door at olivines lighthouse and it will take you to jasmine then go back to the gym then jasmine will battle you
Beat Jasmine in Olivine. Done that then go to Mahogany.
use fire types for her magnemites then use a ground type for steelix
You can find a Steelix in Route 47, Cliff Cave, Mt. Silver, or you can trade any Pokemon with Jasmine.
You can only get the SecretPotion after you have talked to Jasmine in the Olivine Lighthouse. Then she will ask you to get Ampharos some Medicine. You go to Cianwood City and talk to the guy at the Pharmacy and he will give you SecretPotion for Ampharos.