Wish me luck! I have a job interview in a couple hours

I've been underemployed since last year when my previous employer basically told me they had no need for me anymore, and since then I've done a handful of part time jobs. I've been getting a little discouraged because it's been hard finding something full time (I bombed the first couple interviews I went on, the first one because she didn't like the texture of my hair and I was reticent about straightening it -- I'm white but my hair is wavy -- and the second one I dressed too professionally for because they wanted someone trendier) and I haven't had anything else good since then.

This is in an office, and it'll be a foot in the door for a career in HR. I've straightened my hair, I'm not wearing a skirt, and I did all my research. It's a legit company and not a scam or an MLM, so I have absolutely no idea what the hell they're even interested in me for. I am completely freaking out.