You can build bigger biceps by bending your wrists slightly when you are doing arm curls with dumbbells. When your doing your arm curls, extend the wrists backwards slightly, and hold them like that. This slight change of movement will make your biceps work harder, thus, building bigger biceps.
If you are starting a new physical fitness program, the route to success is not to go about it too aggressively. Generally, you are trying to make this a habit, not a regime. Approach a workout or a walk around the block as if it were second nature, like doing the laundry. Just relax and do not be hard on yourself, especially in the beginning.