To lose the fat on your arms, you will need to lose fat all over. This can be done with cardio exercise such as running. Try doing 45 minutes of cardio five days a week. Lift weights three days a week to tone and strengthen the arm muscles. Try to do about 6 different exercises, with 2-3 sets of 10-15 reps. Start with a weight that you can do 10 reps, with the last rep being very difficult.