And, O best of men, I too with innumerable monkeys set out towards the south in quest of Sita, O mighty-armed one. Then a mighty vulture Sampati by name, communicated the tidings that Sita was in the abode of Ravana. Thereupon with the object of securing success unto Rama, I all of a sudden bounded over the main, extending for a hundred yojanas.

In plain words: Hanuman went south with many monkeys to look for Sita. The vulture Sampati told them she was held in Ravana's home. To help Rama, Hanuman leapt across the ocean, a hundred yojanas wide (a yojana is several miles).