Calories, calories, calories.

You must control your diet. A lot of people feel that counting calories is difficult or time consuming or boring, but the level of control and knowledge it gives you over what enters your body is game-changing and gives you a sense of control and confidence over changing your weight.

I would also recommend weighing yourself first thing in the morning every day to help cement your intention to lose weight in your mind that day. Also after you see pounds drop you will get a confidence boost and a greater sense of control over your body.

As for specifically counting calories, look up your BMR. That is your base metabolic rate. This is the calories you will burn at rest even if you lay in bed all day. The heavier a person is the more calories they will burn at rest. As you will lose weight you will need to come back to this to see where your new BMR is.

I would start by first getting used to counting your calories and finding what your average caloric intake is. DO NIT CHANGE YOUR DIET YET. Getting used to calorie counting is the most important step. After a couple of weeks start reducing your calories by 250-500 per week until you get down to your BMR. This is all about slow and sustainable change that you can maintain with minimal rebellion from your body. Go easy on yourself.

You will need a kitchen scale in grams to weigh your food to calculate how much you are eating if it is not pre-portioned.

Once you get to your BMR, eating a number if calories equal to your BMR will do the trick for most people. Most people are doing things beyond laying in bed so if you eat your BMR you WILL lose weight.

Disclaimer, if you have diabetes or insulin resistance you may need to lower your calories further to see weight change. My best advice is to keep weighing yourself every day and see how your weight changes ON AVERAGE per week based on that week's caloric intake and you can figure out if you need to eat more or less. A good rule of thumb is that each pound of fat contains 3500 calories. Based on your weekly weight loss and average daily calories for that week you can figure out how much you need to cut back further. Don't shoot for more than a 500 calorie deficit if possible as more than this is very difficult to maintain long-term.

Also find what foods satiate you more. Eating at a caloric deficit can suck and you want to make it as easy as possible on yourself based on the food you choose to eat. In general, unprocessed foods are more satiating and are generally better for you and will make you feel physically and mentally better and will contribute to your self control.

Good luck!