you dont you go talk to the sailor guy in the house by the sea you find after going through rustboro city.
in rusturf city
All the Pokemon past Turtwig are unavailable in Ruby.
The ruby is in the tunnel behind the team rockets on mt. ember
Its a tunnel that connects the route east of rustboro city with verandturf town.
In venerft town and rustbro city in where the grass is.
Skitty does not appear in Rusturf Tunnel. Only Whismur are there.
skill
Yes, you go into Rusturf tunnel, from the cave entrance in Vernturf town.
There is a tunnel that links them but you need Rock Smash to get through.
You need to have Rock Smash, first. Then, go to the tunnel in Verdanturf Town. Destroy the rocks where the guy and the girl are standing, and he will give you the HM for Strength.
beat the grunts
smash the rock inside the rusturf tunnel that is preventing the 2 people from each other