There are two ways.

1, go on a diet to lose weight first, and lose both fat and muscle. Reduce to the ideal weight, and then start exercising. Dieting, you must eat enough for breakfast, eat apples for lunch and dinner, prohibit snacks and supper, and lose weight quickly.

2, first do aerobic exercise, jogging, aerobic and the like in the gym, don't do anaerobic exercise. Diet must be controlled every day, and supper is forbidden. After reducing to the ideal weight, start to do anaerobic exercise and exercise muscles. In fact, you must have a lot of muscles under your fat now. No need to exercise muscles. Just keep doing aerobic exercise.

Remember to drink plenty of water. Every sentence above is the key point. I wish you success!