Outside Capua they had to good luck to come upon wagons loaded with weapons meant for gladiators in another city so they were able to arm themselves. Spartacus was elected the chief of three captains. It’s possible the other two were Crixus and Oenomaus.
After defeating the Romans who were pursuing them out of Capua, the rebels were able to substitute Roman weapons for their gladiator weapons, which they considered dishonorable. First attacked by the praetor Clodius on a mountain (Vesuvius?), Spartacus’ men were able to escape to the other side, circle around, attack, and defeat the Roman force. After this battle, the rebel force grew stronger though the recruitment of sympathetic allies.