You have to work the whole body in order to lose body fat, the upper arms are one of the hardest areas to maintain, but watch what you eat, drink lots of water, try and walk every day while holding some hand weights, or small dumbbells and exercise 3-4 times a week, try these for your upper arms, Using one of those exercise- rubber stretch bands you can buy, hold one end of the band in each hand with your palms facing each other and position it under your feet. Stand with your legs shoulder width apart and bend slightly forward from your waist with your back straight, straighten arrms so they are out in front of you and parallel to floor. Pull sides of band toward you so your arms go on each side of your waist. Make sure your elbows go past shoulder point, move bande back to starting position, do 3 sets, 20 reps each.

Also try using dumbbells, 2/3 kg. Small weight to start and work up. Bicep curls, tricep overhead extensions, check online to find out how to do these