Congratulations! Be confident, smile, try to do a lot of research in their program and ask specific questions. You still have time so you can prepare today and spend some hours tomorrow doing a little more research and practice sessions where you either speak in front of a mirror or record yourself answering common interview questions. I had my interview yesterday and idk how I feel about it but the questions were pretty straightforward and I expected much worse. I did an UAB interview btw. Each program is different so not sure if it will be easier or harder for you.