After you have defeated all 16 gymleaders, go to Professor Oak and he'll give you the HM.
you can find it in cerulean cave in the northeast corner of b1fyou to have a pokemon that knows rock climb
have a Pokemon who knows rock climb and rock smash
Rock climb
Hes on top of the cave just west of the Pokemon league gotta have strenght rock smash and rock climb
Rock climb is an HM, not a TM, so you cannot just 'find' it. You have to get all 16 badges first, and then Professor Oak will call to give you a gift. The gift is the HM Rock Climb.
you use rock climb
Go to mount silver (With a Pokemon that knows rock climb) climb to the top, and challenge Red.
In the Cerulean Cave, you can find it on BF1 in the north-east corner. You will need Rock Climb.
You need to have the move rock climb
You find HM rock climb on route 217.
Red is at the top of Mount Silver, you need to use the HM Rock Climb to get all the way up to him.
his name is red but hes on mt silver. you need rock climb and tough as crap Pokemon. his Pokemon are level 80 or more. so, ya, good luck!