Since he's here I assume it's cashier. In which case....
"On your first day you'll be doing computer training,
on the second day - computer training,
on the third day - finishing up computer training then sent to the floor.
Once there you'll be given an instructor for about 15-30mins who will quickly go over your responsibilities(leaving lots of things out) and what will be expected of you... then they will throw you to the wolves and wish you "best of luck".
If you have any questions ask the people around you and hope that they know the answer.
If you're in a department and no one around you knows what you need to be doing ask a manager or your department head.
I'm not sure where Bag Boy was trained, but as a Cashier, mine was nothing like that. It was more like:
Day 1 - Familiarizing yourself with the keyboard and basic functions
Day 2 - Familiarizing yourself with more advanced aspects and functions
Day 3 - Reviewing what was learned, and then doing it all for real for the rest of the day
Our instructor was always there to answer any questions and help us out when need be. We never felt like we were "thrown to the wolves", and all of us passed the class easily. The hardest part after training with him was simply remembering produce codes.
To the OP: If you are a cashier, just go into it like you would any other job. Expect to learn the necessities of what is needed, and then learn the rest along the way. You won't learn everything all at once, and you won't remember everything the first few times. The same with any other job. You learn by doing. If your instructor is at all any good at what he/she does, you'll be fine.