My weight is 66kg now. I want to reduce it to 60 kgs over a period of one year from now. Can I do that even my BMI is average? What is the best method

Slow and consistent . Losing 6 kg(~13 lb) over a one year period of time is reasonable. That is only a decrease of about 3500 calories a month or a little over a 100 calories a day. Start by reducing or eliminating any high calorie drinks such as soda, juice or alcohol. Start a consistent walking program, minimize fast food, concentrate on whole foods: lean meat, veggies and fruit. Have a cheat meal every now and then.
Best and healthiest. The best and healthiest way to lose weight is to do cardiovascular exercise for at least 30 minutes 4 days a week. In addition, a low saturated fat diet will help as well.