I think Yeats wrote “The Lake Isle of Innisfree” not as an autobiographical poem, but rather from the imagined perspective of a country peasant. It is probably more correct, therefore, to talk about what the speaker, rather than the poet, plans to do in Innisfree.
In Innisfree, the speaker plans to be self-sufficient. He plans to build his own home, “a small cabin,” and grow his own food (“Nine bean-rows will I have there”). Innisfree is an uninhabited island in Ireland, and the speaker wants to live there alone, implying that he is fed up with people. Indeed, he wants to go to Innisfree because he believes that he “shall have some peace there.” He also expresses a desire to listen to and be at one with the natural world. He wants to live “alone in a bee-loud glade” and listen to the “lake water lapping with low sounds by the shore.”
To fully understand or appreciate what the speaker plans to do in Innisfree, it is helpful to understand what he wants to escape. In the third stanza, he contrasts the aforementioned sound of the “lake water lapping” with the implied noise of “the roadway” and “pavements grey.” In other words, he seems to be fed up with the hustle, bustle and noise of the city, and so longs for the peace and quiet of the country.
The speaker wants to lead a quiet life on the Lake Isle of Innisfree, far away from the hustle and bustle of the big city. Once he's reached his rural idyll, he plans to get close to nature and live off the land just like Thoreau in Walden, a book that strongly influenced Yeats when he wrote the poem.
But first of all, he'll need some shelter. So he's going to build for himself a simple cabin made of wattle and clay. (Wattle is a primitive variety of building material used to make roofs, constructed out of branches and twigs woven together). Once he's done that, he'll grow rows of beans—nine, no less—and build a beehive, from which he will obtain honey.
The poet wants to build a little cabin. He wants to grow a small garden and keep bees. He wants to live alone and listen to the quiet and the sounds of nature, especially the sound of the water.