How do I lose belly fat. I'm happy with my thickness. I just want to lose the belly and fat around my mid section. And maybe alil on my thighs.?

Spot fat loss does. not occur naturally. By losing weight in general some will probably be abdominal fat. But, we don't get to choose what area of body fat is lost from. Eat healthy & be physically active. Calories burned must > those consumed. Tighten ab's: crunches, reverse crunches, exercise ball crunches, pelvic thrusts, lying leg raises, side bridge & “bicycling” exercise on back. Do regular aerobic exercise.
Weight loss. You can't spot reduce fat, so there is no way (besides surgical liposuction) to target specific areas for weight loss. The best option is a healthy diet and regular exercise to lose weight and as the pounds come off you'll notice a difference in those areas of concern.