The phrase "to light the bonfires" means to start or ignite a large fire in an outdoor gathering, typically for celebratory or ceremonial purposes. Full definition
«How, sir, would you make a ship sail against the wind and currents by lighting a bonfire under her deck? (inc.com)
«June solstice traditions around the world include lighting bonfires, as fire was believed to scare off beings of the night — both real and magical. (inc.com)
The night of November 5 is now Guy Fawkes Night in England, a holiday celebrated in England by people lighting bonfires and fireworks, along with burning an effigy of Fawkes, to commemorate the failure of the plot. (religion.blogs.cnn.com)