AI am new to this and I've attempted to google but I keep getting anything and everything that I DON'T need. When buying premade icing how do I know which one will crust?! Can I even buy the kind that will crust or do I just have to make it?

AIve always made mine, simply because of taste. Not saying there isn't a store bought that isn't good, but i haven't found one. I sometimes think they're more expensive too. I'm not a professional by any means, just a casual at home baker. But, I have done some trial and errors and know what I like and can count on it.

store bought icing does not crust. You are much better off making your own. There are several here on CC- just search - Crusting Buttercream. It takes less time to make than to open up a can:)