How does Guilliver get to Brobdingnag?
The story of how Gulliver gets to Brobdingnag is found at the start of Part II. Basically, Gulliver gets to Brobdingnag in much the same way he got to Lilliput; by bad luck on a voyage to somewhere else.
This time, Gulliver is on a ship headed for India. However, the ship is blown off its course by a storm. The ship ends up sighting an island and Gulliver and some others go ashore to look for water. Gulliver ends up getting left when a giant chases the other men back to the ship and the ship sails away. Gulliver is left on the island which is, of course, Brobdingnag.