Ok ive got about 20 to 30 minutes at home a day. I have a floor a pair of 8 lbs dumbbells and a window sill that i can put one knee on. I am 14 and 110 lbs... Im short and skinny my arms are puny my pecks are pathetic and small my shoulder blades stick out of my back. Im not really concerned with my legs or stomach right now. Just arms shoulders and back. What should i do. Im sick of being so puny i know it will take time but i dont care i really just want more mass. Thanks