Run claude and you'll see a prompt. Type a task the way you'd describe it to a developer: "Find all TODO comments in this repo and list them by file" or "Write a Jest test for the parseDate function in utils.js".
Claude reads the relevant files, tells you what it plans to do, and asks for permission before making changes. You'll see its thinking inline. Each response ends when Claude is done or waiting for your input.
One habit that pays off quickly: be specific about scope. "Refactor this function" is vague. I find "Rename the parameter from d to date and add a JSDoc comment" gives Claude something precise to act on.