NEW RETAIL JOB?! & SOCIAL ANXIETY?!

I have no experience what so ever. I am kind of a shy and nervous person until I’m comfortable and my previous job experience was professional cleaning for a construction company so I rarely had to deal with any people. I just got a call back from a small retail clothing store and they asked me to come in tomorrow for 3 hours to meet the owners and be taught some things and then they will decide if they want to keep me.. I have no experience on the cash register or any of that and have a feeling they will just be throwing me in to see how well I do. Does anybody have any tips or advice for me? I’m almost positive I have social anxiety because I don’t like being around new people so I am EXTRA nervous for how tomorrow will go. I know I need to face my fears but my heart is beating out of my chest so bad rn lol please advice anybody?!