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.