You have clearly asked a big question here - the majority of poems use a number of figures of speech, and so rather than go through each separate example, I will identify a few and then hopefully this will help you to be able to go back and analyse the poem further.
To me, one of the most powerful figures of speech lies in the last few lines of the poem, where two similes are used to show us how we should approach death:
Thou go not, like the quarry slave at night,
Scourged to his dungeon, but, sustained and soothed
By an unfaltering trust, approach thy grave,
Like one who wraps the drapery of his couch
About him, and lies down to pleasant dreams.
Note how these examples of figurative language are tied in very closely to the theme of the poem - we must approach death with confidence and trust, safe in the knowledge that we are going to re-join with nature. The last simile in particular is key in presenting an attractive image of someone who has worked hard and is now merely getting the sleep and rest they deserve after their toil, enjoying "pleasant dreams."
Hope this helps! There are plenty of examples to pick out, and you might want to think about the personification of Nature as a starting point. Good luck!