How can I build my arm muscle at home without paying anything?

I’m a 14 year old girl, and I want to start building arm muscle…it looks like I have a pretty good “bulge” of muscle in my bi-ceps, how can I build it quickly at home for no cost?

Get one of your dads shoes, and use like a dumb bell, just lift it up above your head and back down to your waist level.
I bet you cannot do 200 with each arm!

Arm Muscle Exercises : The Dumbbell Concentration Curl Arm Exercise