Presumably, you've just read this book and should be able to find these examples.
These sites may help you.
Alliteration is the repetition of sounds at the beginnings of sequential words, and these sounds are almost always consonants.
In that poem (line 3), you'll read "rifles' rapid rattle" -- an instance of alliteration of the initial r-sounds, intended to imitate the harsh and fast sounds of bullets firing.
Assonance is the repetition of vowel sounds in a sequence of words. One of the best examples I've heard is the name of a dessert ~~> Jumpy Monkey Sundae! Even though the actual letters are u-o-u and y-ey-ae, the vowel sounds are the same. In fact, this example seems to be an instance of double assonance, if you will!
Now read through your book and see where you come across these types of sounds. You may need to read sections of it aloud.