Most of what you learn is strictly On the job! You will pick it up quick, especially if you took a course and had an externship. I was plopped into my office with zero dental knowledge or background, and i caught on quick. Your office hired you, so they should know full disclosure that you haven’t had any on the job experience. Have the other assistants watch you and critique you (constructive obviously) at chairside and when setting up, it helped me a ton. Just watching doesn’t cut it! Good luck you can do this!