Hearing everything from me the lotus-eyed Rama at once ascertained his course of action, and having for the passage of his army constructed a bridge across the deep, crossed it followed by myriads of monkeys. Then by prowess Rama slew those Rakshasas in battle, and also Ravana, the oppressor of the worlds together with his Rakshasa followers.

In plain words: When Rama heard Hanuman's report, he knew what to do. He built a bridge across the sea, crossed it with a huge army of monkeys, and killed Ravana and his Rakshasa (demon) armies in battle.