I feel like such an idiot?

ok, so i got this job at a christmas store doing overnight stocking(this is after being fired from toys r us after 3 days;same type of job) so anyway yesterday was my third day on the job and the ''lead stocke''r was training me. all she was doing was yelling and me and making me feel like an idiot. supposedly everything shes saying is common sense but i just cant comprehend or grasp any of it. am i an idiot. all the people i work with are like bums and minority, and they all joke about iu have to be an idiot to not ace this job and its demeaning to their intellect lol. what do i doo