The focus when working on specific muscles is learning how to isolate it. Whether you prefer dumbbells or bands you want a variety of angels when working the biceps.
We are going to do bicep curl. You can do this movement at home with your own weights or in the gym. We are going to lock our elbows to our side, bring both dumbbells down and up at the same time. With your elbows locked at your side, you want to keep a controlled motion by doing these movements slow while extending your arm fully with a slight bend in your elbow still and flexing as close to your body as possible. The most you want to get out of this workout is two sets of 20, the weight you use will depend on where you are at physically.
When you're in the gym and using cables or bands you want to have constant resistance. For cables, you adjust the machine to be closer to the ground and you pull the bar up towards your chest with your palms facing up but your hands closed. You can use the band for almost the same motion. The bands are different colors for different resistance, but keep it at your level. Bring the band towards your chest squeezing the biceps..
You want to get the arms fit and firm. Then blast those biceps!