Desperately need help in learning how to take blood pressure?

I am being very discouraged. I just can't seem to get it. What I am having the most trouble with is when you have to listen in order to measure the blood pressure. I still don't understand what I am supposed to be listening for!! I am sooo frustrated I really just want to cry and maybe even change majors because of this.Desperately need help in learning how to take blood pressure?
Blood pressure is composed of your systolic reading (highest pressure when the heart ventricles pump) and systolic (the pressure when the heart is at rest) When you put your stethoscope to the antecubital fossa (AC), and pump up your cuff to say 160 or 170 and you release the dial (SLOWLY) and you hear the first beat that is your systolic reading...when you hear the last beat that is your diastolic reading. Say I start at 170...release the pressure slowly and my first beat is at 120...and my last best heard is 80... and in between 120 and 80 I hear beats, my BP would be 120/80.