Can anybody help me thicken/widen my arms, please?? ?

Alright, so here's my issue. I'm 15 years old, 5'6 or 5'7, and weigh in at around 125+/-I have a nice body frame, but my arms are rather small no thanks to my triceps, measuring around 9 or 10 inches when measured with measurement tape. How freaking smallllll!!? What tricep exercises, meal plans, and whatnot would really bulk the **** of my triceps area so I don't have to hide in long sleeved shirts anymore such as in the hot sun as I have been doing for years. I'm so embarrassed and saddened when I look at how twiglike my arms are. I have nice pecs, and a flat hard stomach, and such but i hate having to not enjoy the freedom of wearing only a muscle shirt or t-shirt. Someone please help me. I wanna have massy bulk filled, cut, strong *** arms. Please please please help me. Summer is very near and I get embarrassed at the beach in a muscle shirt. Please anyone, help me out. I beg, but with my dignity. I want thick, bulky *** triceps. Help me? :l