Let's practice three examples of how you can make a device into a cogent point of analysis, shall we?  (Like you have a choice in the matter.) 

For each instance, draft a couple of sentences --however many it takes -- that get us from Point A (a quotation) to Point B (an endpoint of analysis).

1.    From...  

The grey sea and the long black land;
And the yellow half-moon large and low  ("Meeting at Night")

    to...  "This is how the alliteration displays the distance which opens Browning's poem."

2.    From...

Ah, little dark girls who in slippered feet
Go prowling through the night from street to street.  ("Harlem Shadows")

    to...  "These lines demonstrate how McKay's diction conveys his attitude about the streetwalkers' plight."

3.  From...

"Brings me yew to deck my grave"

    to... "Blake ignores part of the symbolism of the yew tree, then, to emphasize its connections to death, the "end true lovers have" in this poem.