The speaker of the poem fantasizes about leading a life of quiet repose in the wilderness. At the time when Yeats wrote "The Lake Isle of Innisfree" he was heavily influenced by Thoreau's Walden, with its ideal of a simple, self-reliant lifestyle pursued amidst natural surroundings. During his stay at Walden Pond, Thoreau grew beans, which symbolize the wisdom of an austere life lived in accordance with the primal rhythms of nature.
In the relevant chapter of Walden, Thoreau says that he was "determined to know beans." This is a humorous reference to the expression "to know beans," meaning to know very little. What Thoreau is acknowledging here is just how little he knows about life in the wilderness. Thoreau comes from a long tradition of thinkers—of whom Socrates is a notable example—who believe that true wisdom only begins with an honest confession of ignorance. And it is just such wisdom that Yeats wishes to cultivate—along with his rows of beans—on Innisfree.
As regards to honey, this is an example of the speaker's desire to live off the land. He yearns for a completely natural existence, and what could be more natural than the sweetness of the hive? There could also be some religious symbolism here. John the Baptist famously lived a holy life in the wilderness, living off wild honey and locusts. The speaker could be seen as trying to emulate his example, insofar as he seeks to live a purer, more natural life, far away from the hustle and bustle of the city.