Hi Mridula,
Doing nay activity which includes just spreading a bed sheet will also burn calories might be quite less but it will burn. You can inrease fat burning process by doing more of weight training exercises along with cardio exercises. Weight training exercises will help to build up muscle mass which means that it will help to improve you BMR and thus would burn more calories. Also, cardio exercisse has proved to be very useful for the persons who are looking for reducing body fat percentage. You need to do weight training exercises atleast for 20 min every alternate days and cardio possibly every day or atleast 5 times a week for better results for 45 min per day. This type of exercises will help to reduce your body fat percentage and loose weight.