I got written up at work? HELP! Full Points?

This happened to me when I started working at a store. I think it is very common, and since you were brand new to the register, the manager most definitely knows you did not steal. Most people go through it, and they're talking about you being written up because they probably have to and because they want you to take the job seriously. So, you are handling this correctly. I would even ask your manager for more training if you aren't comfortable, which is only fair.