This exercise will add mass to your upper arms by working the bicep through a full range of motion. This movement will also work the forearm like any other curl movement.
Begin standing with a dumbbell in each hand, palms facing your body. Next, contract the bicep muscle and pull the forearm to the shoulder. While doing this you should also rotate your wrist so that your palms are facing up at the end of the movement. This will help to peak the contraction of the bicep. Hold the contraction at the top of the movement and then slowly lower the weight back to the starting position. Repeat as many times as necessary to complete the set of repetitions.
There are a ton of variations to the dumbbell bicep curl, many more can be found on this section. One would be to start with the palms facing up and eliminate the rotation throughout the movement. Another would be to keep your palms facing inward towards your body throughout the entire movement; this is called a hammer curl.
Many beginning lifters do too many bicep curls, you should aim to work all of your muscles the same. Most lifters want big arms, but do not overtrain your biceps or else they will not grow.