Show up with long sleeve shirt or jacket, boots that cover your ankles, gloves, and a good attitude. That's all you need. They provide helmets and motorcycles. If you have your own helmet bring it.
They teach you EVERYTHING, if you don't pass you either have no business on a motorcycle or didn't listen very well or try in the least. It is set up for you to succeed. They gain nothing by you failing and have no reason to fail you unless you MAKE them.
It's also a BLAST if you've never ridden.