Students are often particularly concerned by unseen poems and the reason is obvious; you've spent months annotating your anthology booklets, drawing together comparisons and remembering a whole range of technical terms, and now you have to do the same exercise without any support. However, the comforting thing to remember is precisely that: it's the same exercise!
All the names of poetic devices, your understanding of tone and how it is achieved, is going to be assessed again in exactly the same way. The examiner is still looking to find in your paper:- an understanding of what the poem's literal meaning is, what themes this explores, what effect this has on you, and how the poet achieves this effect (this is where your well revised terminology comes in handy). Give a well-structured account of these four considerations with an introduction, main body, and conclusion, and you will be well on your way to a good mark!