Follow these steps:
1- Find out the number of calories your body needs. For this, you can find calories calculator online. Just put in your age, weight, and height. It will give you a number. Multiply that number by your activity level. To find how many calories you need. Go here
Calorie Calculator
2- Install MyFitnessPal app in your smart phone, and track how many calories are in each thing that you eat. It will not be 100% accurate, but it would be a close proximate. Now Reduce 20-25% of calories from the total needed. For example, if you need 2200 calories everday (From calculator), reduce 25% or 550 calories. So your goal should be to eat around 1650 calories everyday. YOU MUST STICK TO THIS. NUTRITION IS NUMBER 1 PRIORITY. IF YOU GET THIS STEP WRONG, NO MATTER HOW MUCH YOU EXERCISE YOU WILL NOT LOSE WEIGHT. Also, you can eat whatever you want in a day, so long it is within your daily calories goal (In this case, 1650 calories). It is better to eat healthy, but for starters, eat what you like within the calories limit. Keep in mind that you don't want to eat too little either. If you each too little, you will feel like shit and your body would start to eat muscle and you will gain fat eventually.
3- Do cardio exercises 30 minutes 5 to 7 days a week. This is also a must. Because with diet alone, your metabolism remains slow. This will help decrease fat rapidly. Cardio exercise can mean walking, running, jogging, cycling, swimming... Any continues physical activity that keeps your heart rate at 70% of maximum (read more about this)
For further details, I highly highly highly recommend a book called "Burn the fat, feed the muscle".
I am in a hurry, if you want to ask anything else, you are most welcome.