You use HM6 Rock Smash.Which you get in jubilife city in the cave after you get the poketch
Chat with our AI personalities
You need to beat the first gym and teach a Pokemon Rock Smash(Machop, Bidoof or main Pokemon and then you talk to a rugged rock and it will say "Would you like to smash it?" choose YES and, POOF, it's gone.
HM06 Rock Smash
Get the HM Rock Smash
you must HM rock smash.
You get the HM rock smash and teach it to one of your Pokemon. You get it on island 1.