Interviewing for job outside of field of study


What do you do when you are about to do this:

I am about to interview for an assistant production supervisor position for a place that makes candles. Even though I’ve been mainly looking for work in Accounting. But I’ve read the job description and it looks like I could learn alot of other valuable work skills. But I’ve never been in any kind of supervisory position before and I would struggle to come up with an answer to the dreaded “why should we hire you?” question. Most of the job responsibilities are vague or difficult to understand.