I have a big belly what can i do to reduce it?

The basics: If your big belly is not from bloating or constipation (stooling 1-2x per day), then getting back to the basics is advised: lifestyle and diet. I recommend starting with the paleolithic diet and doing interval training for 4 mins per day (google tabata burpees).

Weight loss: Exercise (walking, pool aerobics are good because there's less stress on feet, ankles, knees, hips) and portion control to reduce caloric intake. Eat lean meats, fish, plenty of fruits & veggies, limit high glycemic index carbohydrates, use good fats (unsaturated), whole grains. Use a salad plate instead of a dinner plate; no second helpings. Try 4-6 "mini meals" instead of 3 big ones. Limit alcoh.