The speaker says he's going to go to Innisfree to build a small, simple cabin. He'll have a little bean garden and a honeybee hive. He wants to live alone in peace with nature and the slow pace of country living. Sounds like a plan, buddy.
In the last stanza, the speaker restates that he's leaving and explains it's because every night he hears the water lapping against the shore (of Innisfree). Even though he lives in a more urban place with paved roads, deep down inside he's drawn to the rural sounds of Innisfree. It's all about rustling trees, not bustling buses for this speaker.