Switch your dairy to low-fat
or fat-free, eat lean meats whenever possible and reduce your processed/
fast food intake and you'll reduce a lot of the unhealthy fat from your diet.
Even though you're thin, cardio is still important for overall health so you can do any kind of cardio you like 4-5 days a week. Some kind of strength training 2-3 days a week will help you build muscle and help tone up the areas you want to.