The key to weight loss is consistency. You need to be in a calorie deficit. Google tdee calculator and this tells you your daily calories to maintain. Take off 500 calories and you will burn 1 pound per week. As you want to lose 6.3 stone that equals 88 pounds. So it would take 88 weeks to lose the weight. You could have a greater deficit and lose weight quicker. I would suggest logging food and exercise on myfitness pal and regularly weighing yourself to monitor progress.