mauville city
at the gym
the ground gym
it's in the woods between the first gym badge and 5th gym badge
you build up your Pokemon higher than the gym leaders and the you kill the gym leaders Pokemon and as they all faint you will get a badge and you have to move on to nuger 4 gym leader
Beat the gym leader
Pokemon league
The only way to get a gym badge is to challenge the corresponding gym leader and win.
by beating the fourth gym leader
Uh what are they and what levels?
it is Mauville gym
just go to the gym and beat Watson with his electric Pokemon
Flannery, a fire type gym leader.