I want to improve my biceps size?

Biceps: Try lifting weights in the sitting position and do exercises for the upper extremities.

Curls: Use dumbells stating at low weight of 8-10 lbs. Initially. Doing 2-3 sets of 10-12 reps of simple curls for 2 weeks; thereafter increase by 5 lbs/week until complete exhaustion of muscle : not severe pain-weakness. Start as low as possible. Ok to use low weight kettle balls- but more costly. Form and technique are more important than weight , next move to hammer curls.

Bigger biceps.: Three exercises to research for a bigger biceps will be barbell curls, dumbbell curls and slide curls. While slide curls should be done with lower weights, dumbbell curls and barbell curls can be done with heavier weights. Choose a weight that allows for 8 to 12 reps before muscle exhaustion sets in. Three sets of each exercise once weekly.