Flannery, a fire type gym leader.
by beating the fourth gym leader
The fourth one.
Take cable car and move downwards. U will reach the town.
Go to laverigde town, and beat flannery, the 4th gym leader. Be sure to bring a water, ground, or rock Pokemon with you.
at the gym
Go to the Pokemon league.
the ground gym
Dewford Town.
Destroys picachew
island? the fourth badge is in celadon
Beat the gym leader
you travel to lavavine town