What to do when you are being interviewed for a job you feel underqualified for?

I have an interview for a job. I feel like this job is much bigger than me, but that I could perform it very well if given the chance. It required a masters degree and 3 years experience. I have that degree, and my experience can be tailored to fit. I am young and fresh out of school. I am afraid in the interview they may take one look at me, or hear my experience and think its not enough. How do I sell myself, so that I don't look like a complete idiot?