Don't worry. In fact, breathe a sigh of relief. This is one poem that you can read aloud without any worry about how to pronounce things correctly or any trouble putting the emphasis on the wrong sy-LA-ble. In fact, not one word in this entire poem is longer than two syllables. And to make things even easier, Millay has created four end-stopped lines, which means that her punctuation (in the form of semi-colons, dashes, and so on) tells us exactly when to pause (at the end of the line, of course).
We're keyed in to the fact that Millay is a fan of the alliteration before we even get to the first line—the title, "First Fig," has two glaring F's in it. And once the poem gets going, the alliteration keeps coming. First there's the "foes" and "friends" pairing in line 3, and then, of course, we end with the "lovely light" in line 4. Put all those examples together, and we've got a pretty good case for alliteration as Millay's favorite literary trick.
There's something playful about the word pairings, as well. Why, for example, would foes and friends be used together? Why not, say, enemies and friends? We're betting that alliteration helps Millay create the sense that both her foes and her friends are, for this one moment, connected, both in their sonic similarity and in their utter awe at her awesomeness. Connecting them one way is a pretty good way to point out to the readers that she's hoping to connect them as an audience, as well. And it works.