OK, the way to answer this is to go back to the text and find those passages that pertain to competition. A list of pros and cons is a great tool for organizing what you know: write out quotations that would support the argument that children have a naïve view of competition under "pro," and write out quotations contrary to that argument under "con." Don't shirk this preparation work. This list is your knowledge base; it represents
what you know about the subject.
Compare and contrast the quotations in your list of pros and cons. Are there more quotations for or against the argument? Are there quotations that carry more weight than others or speak more specifically to the argument? What do they actually say? What reasons do they give? Based on what you understand, choose to argue either for or against the idea that children have a naïve view of competition, and choose the best quotation from your list to be your evidence. (For a short answer you only need one, but for an essay you might use three.)
Now, using your best quotation, explain how it supports your position. In paragraph form: state your position, introduce your quotation as supporting evidence, and then explain how and why your quotation supports your argument.