The key section of this poem that you would benefit from focusing on comes in the second stanza, as Nature begins to describe its plans for Lucy and the kind of intimate relationship that they will enjoy together. Consider the kind of language that Nature uses to describe this relationship:
Myself will to my darling be
Both law and impulse: and with me
The Girl, in rock and plain,
In earth and heaven, in glade and bower,
Shall feel an overseeing power
To kindle or restrain.For me, the most important part is when Nature says it will be "Both law and impulse" to Lucy. This is a key Romantic idea, as Wordsworth and other Romantic poets argued that growing up in society actually acted as a barrier to Nature and the kind of intuition that was so important in order to be open to Nature and the beauty and wisdom that it contains for us all, if we but have eyes to see it. The stanza also refers to the "overseeing power" of Nature that is available to us. Nature therefore educates Lucy primarily through developing her powers of intuition and keeping her from growing up in the world of men to become deadened to Nature's power and influence.