In an analytical essay, you will need to present an argument, or claim, for some feature of the text. You might want to first begin with a question. Here are some ideas that might work for Where the Crawdads Sing:

• How does the setting impact Kya's character development?
• How is the setting both a source of conflict and of peace for Kya?
• How is Kya's experience an indictment against the traditional educational system?
• How does Kya change over time?
• How is Kya's sense of loss linked to the sea?

You'll want to center your questions around the structure of the work, its character development, or literary techniques the author uses to create depth in the plot and characters.

Once you find a question that seems meaningful to you, you're ready to begin formulating a thesis. At this point, you start brainstorming possibilities for your answer that you could use in the evidence (or body) section of your paper, and a thesis will likely begin to emerge. Here are some examples for some of the questions above:

• Kya's experience shows that interest and enthusiasm for content are the best predictors of educational success—not a specified number of courses in a traditional school setting.
• The setting becomes both a source of pain for Kya as she is never accepted among her fellow citizens and a source of comfort as she finds peace in the isolation of marsh life.
• The marsh setting provides Kya with the nourishment she needs to survive, a sense of permanence which she lacks in almost all human contact, and the possibility of beauty in life, and these provisions shape her character as she becomes a fully competent and strong woman.

Once you have your thesis squared away, the evidence for that argument should fall into place.

I am linking the analysis for this novel's study guide below for your further reference. Good luck!