How should I approach the unseen poetry?

the old SLIME and PEE would seem to apply;

SLIME referring to "Structure, Language, Interpretation, Meaning, and Effect" as a way to approach analysing the poem, and PEE meaning "Point, Evidence, Explain" as a way to structure your response - having each paragraph (or where applicable, sentence) beginning by stating the point you're making (from your SLIME approach), referring to the evidence from the text (quoting the relevant line etc) and then explaining how the evidence supports your point.

While you will likely extend your response beyond this, as a starting point this is a useful structure to work with for unseen texts so you're not completely dropping in out of the blue