Usually a sign of loose skin, use a firming lotion like Nivia Toner Moisturizing Lotion
There are a lot of exercises that can help eliminate arm fat. Check out YouTube for free videos. Google something like "exercise to lose arm fat" or something like that.
If you google blogilates arm workout there is a great one. Some of the exercises seem odd but I did it and for the first time ever saw muscles in my arms!! I could see them later that day. It's hard but imagine if you did it even just a couple of times a week. I want to build up to doing it daily