HELP! I am just starting as a bagger at a grocery store and I am so nervous!?

i have been dying for the last hour freaking out about this. I know its not a big deal, but i get nervous about everything! about how many items do you put in a bag? what order do you put them in? what happens if I mess up? AAHH omg i am freaking out! please help me with what you have to do and try to cam me down! thanksssss