Adjust seat so that it is not so low that the shoulders are elevated nor so high that you are hunched over the pad. Position elbows on pad, and grasp bar with an underhand grip. Raise the bar until elbows are fully flexed with the back of the upper arms remaining on the pad. Lower the bar until arms are fully extended. Do not allow muscles to relax before next repetition.
Here are a few suggested alternative exercises:Arm Curl - Hammer StrengthBall Dumbbell Concentration CurlBand CurlsDumbbell CurlEZ Bar Curl