how has the narrator, robert walton, prepared for his great enterprise? what gives him the idea?

Walton is a well off Englishman. He has a passion for exploration, which at that time, meant sea voyages. Walton is captain of a ship entering a very dangerous voyage to the North Pole. No, it isn't to look for Santa Clause. He describes a burning desire to accomplish "some great purpose". More specifically he wants to discover a northern passage to the Pacific, revealing the source of the Earth’s magnetism, or simply setting foot on undiscovered territory.