Here's the relevant portion of the text:
"I was saved from sin when I was thirteen. But not the way most children are saved, with a sudden flash of light and a feeling of overwhelming joy. It was a gradual process that took place over a period of several years. It began when I was about eight years old."
This paragraph establishes the main point of the essay: that the narrator's experience of being "saved" was not the traditional, ecstatic one often portrayed, but a more subtle and gradual process. This sets the stage for the rest of the essay, where Hughes explores the complexities of his religious experience and the societal pressures he faced as a young black boy in the South.