Working as a cashier

So I recently got a job working as a cashier in the front counter of a fast food restraunt. All my coworkers treat me like I'm dumb and they are mean and yell at me a lot. I guess I try to understand because I'm new and I don't know what I'm doing yet. But they act so annoyed when I ask for help so sometimes I try to do it on my own and then I mess it up and then they get more annoyed at me. And because of this I get paranoid and nervous which makes me mess up even MORE! I don't know what to do, I hate just standing around doing nothing while everyone is working hard but I would honestly just get in the way if I tried. I feel like they talk bad about me and thy don't even try to hide it from me. It's been my fourth day working and I feel so stupid.