The Big Book is not written entirely like a textbook. The material on Step One is scattered throughout the first few chapters and into the chapter We Agnostics.
There are various aspects to Step One: the physical craving, the mental obsession, the fact there is no such thing as a safe slip, alcoholism's fatal, progressive, and incurable nature, unmanageability, uand the fact that, for most alcoholics, a spiritual solution is required.
This little spreadsheet may help locate where these quotations are. You can use the filters at the top to select particular topics.
https://cutt.ly/BigBookStepOneQuotations