How to slim down chubby arms?
You'll want to do cardio and some other exercise that improves arm muscle tone to slim down chubby arms.
Things like these to build muscle tone: bicep curls chest presses bench press
And then cardio like this; Running Walking Jogging Swimming Tennis Cycling Stair master Treadmill etc, etc.
Good luck getting in better shape!
by swimming one can tone his arms..