You have asked a very broad question concerning the entire length of this rather complex poem. I am going to focus on one section of this poem that gives such a rich and disturbing psychological insight into one man's desperate desire to possess another human creature completely and utterly:
That moment she was mine, mine, fair,
Perfectly pure and good: I found
A thing to do, and all her hair
In one long yellow string I wound
Three times her little throat around,
And strangled her. No pain felt she;
I am quite sure she felt no pain.
As a shut bud that holds a bee,
I warily oped her lids: again
Laugh'd the blue eyes without a stain
This quote is significant for a number of reasons. Note the repetition of the word "mine" indicating the jealous possessiveness of the narrator. His desire to possess forever someone who is "Perfectly pure and good" leads him to strangle his lover with her own hair. Note how the metaphor transforms her golden hair into "one long yellow string." We are also given an insight into the mind of the narrator, suggesting that he may actually be an unreliable narrator, for he thinks that she experienced no pain, the repetition of this statement perhaps suggesting internal doubt. He uses a simile to describe how he opens her eyes, "as a shut bud that holds a bee," which again is another comparison to an act of possession and ownership, which is what this complex poem explores through the poetic devices employed.
I hope this helps give you an example of how poetic devices are used in one section of this poem. Now go back and read the poem again, using my response as a basis for analysis of the rest of the poem.