One of my (dearly beloved) instructors as a student made the comment, when someone expressed concern over feeling like she wouldn't know everything she needed to be a staff nurse, "You definitely won't. You will know enough to be educable when you begin, and you will learn the rest in your specialty."
I actually took some comfort in this, and over the years I've realized how true it is, and how it's not only true of new grads- few if any nurses, even those with years of experience, know enough to thrive in every specialty without additional training and education, even if it's informal and on the job. Nursing school and licensure is there to ensure you have a base of universal knowledge- anatomy, physiology, pharmacology, pathophysiology, and nursing theory, along with a few basic tasks- things that will mean you aren't totally at loose ends when you're handed to a preceptor- you will understand their rationales as they teach you, you will be able to comprehend the whys behind the whats and hows of policies and procedures. Everything else will be- almost must be- picked up as you go.
Pay attention, look things up, ask questions, don't be afraid to admit when something is new or confusing to you, and you'll be fine.