Don't worry about correct format.
Include the text (imagine it being read aloud), and the sounds indicated by the text, but also do your best to convey the mood/content of the illustrations with ambient (ex: rain) and musical beds (a loop or track of sound that plays underneath voices during spoken elements) and discrete, discontinous sound effects (ex: a dog bark or a gun shot).
Search the illustrations for sounds NOT announced by the text. Be as specific as possible i.e. don't just say "opening music," name a particular song, and if a "monster" is roaring, as in Sendak's Wild Things, precisely indicate what sound you'd use to evoke it (don't just say "roar.") Be creative. For instance King Kong was famously a mix of a tiger growl played backwards and a lion roar played forward; the Rancor in Empire Strikes Back was a slowed-down chiwawa, and the velociraptors in Jurassic Park were, at various points, a horse breathing, a goose hissing, and a tortoise having sex.
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