Naturally there are two key ingredients to weight loss: a healthy diet and exercise. I think exercise should usually be increased gradually. The more success you have, the more you will become addicted to continuing your exercise, so there is no need to rush into a heavy exercise routine immediately. Apps are great for tracking your progress and providing motivation to continue. Nutrition is probably even more important though. Remove processed food and excess sugar and fat from your diet, switch to fresh vegetables and fruit (5 a day is a good target) as well as wholegrain/wholemeal products. You'll find way more info on the web, but a good understanding of nutrition is the best way to long lasting success.
Walk everyday, do stretches to your lower abdomen, drink only water, no soda at all, and no sugars. When your doing your stretches just lay on your back and lift your legs slowly to your chest and all the way back down. It'll build your abs muscles. And take up dancing. I've tried this and I lost 9 pounds in one week.
Do not eat fast foods. Eat salads and eat foods with low fats. DO NOT SKIP ANY MEALS. Exercise try running a mile and add to it every time. Try lifting weights and doing crunches. Try switching sodas and juices with water. It will take a few months to lose 72 lb.