Yes, I am very stupid. I don't know where to find Rock Smash.

for Heart Gold - HM06 Rock Smash is found directly west from Violet City, to the east of the Odd Tree which turns out to be Sudowudo. Talk to the fat man looking at the spot where the Sudowudo is and he should give you HM06 Rock Smash.

for Emerald-To get HM06 Rock Smash, you need to go to Mauville City, go inside the house right of the Pokemart,talk to the professor and you get the HM06 Rock Smash

for Platinum-go throw route 203 around Oreburgh City enter the cave opening a Hiker on the left will automatically will give you rock smash..

for Fire Red-When you get to one island go north all the way to the ember spa. Enter the ember spa and talk to the old man. He will give you the HM06 containing rock smash but you MUST Defeat the Elite Four

and no you are not stupid..somethings in the game can be complicated