The quote I think you are referring to comes from an article from 2002 in the Washington Post. I did Google Search: "'answer to anybody' bush" and one of the first hits was this site:
http://www.dissidentvoice.org/Aug04/Samples0824.htm.

The author starts the article with "George W. Bush once told The Washington Post's Bob Woodward the great thing about being president was that he didn't have to answer to anybody. 'I'm the commander,' Bush bragged. 'See--I do not need to explain why I say things...Maybe somebody needs to explain to me why they say something, but I don't feel like I owe anybody an explanation...'"

The actual Washington Post article the author quotes I found by doing a Factiva Search in only the WashPost using keywords "i'm the commander". This led me to the Woodward interview. It's from 19 Nov 2002, page A1. The article is too long to post here, but I will e-mail it to you for your reference. The author from "Dissident Voice" article does quote the Washington Post article correctly, so I guess you can use either one for your essay.