Go to the Elite 4, and beat them.
If you mean "Is Juan the leader in Pokemon ruby?", then no. It's Wallace who's the leader. Juan is leader only in Pokemon emerald. The champion is Wallace in Emerald, but Steven is the champion is Ruby and Sapphire.
you only have to beat the elite 4 on Pokemon fire red not ruby
by fighting
I believe you have to talk to Wallace
new mauville after you get a key from Wallace
In the 8th gym. he is the gym leader
Wallace is the champion. you will find him after you beat the elite4
you play it
In Pokemon Ruby, Wallace is the gym leader of Sootopolis City. When the player first arrives in the city, Wallace is not at the gym. He and Steven are north of the city. They take the player to the Cave of Origin where Groudon is encountered. After this battle, Wallace can be found and battled in the Sootopolis Gym.
Go beat Wallace in Solstice city.
He is the sootopolis city gym leader.
The Pokemon League