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
Wallace is the champion. you will find him after you beat the elite4
In the 8th gym. he is the gym leader
I believe you have to talk to Wallace
by fighting
new mauville after you get a key from Wallace
you play it
Go beat Wallace in Solstice city.
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.
He is the sootopolis city gym leader.
The Pokemon League