How do you get rock smash on pokemon leaf green?

How do you get rock smash on Leaf Green? URGENT!!!!

Hi,

Surf in the northeast direction from Pokemon Center. You'll reach land almost immediately.

In this area, known as Kindle Road, you'll be battling trainers and catching Pokemon. There are Itemballs behind breakable rocks, which can be broken using Rock Smash.

Head north and enter the Ember Spa. Inside is a hot spring where you can heal your Pokemon by dipping yourself in the water. Talk to the old man next to the waterfall to get HM06 - Rock Smash.