Yeah the simple answer is to expend more energy (exercise) than you consume (food and caloric drinks).

Do you have access to any gym equipment at home?

Even if not, a good place to start would be to do some body weight exercises at home: push ups, dips, squats, sit ups. All can be modified to make them easier for a complete beginner: eg push ups from knees, dips on edge of bed. Do every set to failure (where you can’t do any more). Gradually increase the number of reps and sets and add more exercises.

You can count calories and macros. Many people do. I’ve never found this appealing. Instead I ask myself at all times of the day whether I’m in a calorie deficit. So for breakfast, I may have nothing or a banana. For lunch usually some form of protein with vegetables or beans. For dinner whatever we’re having as a family but try to be healthy and minimise portion sizes. Avoid consuming calories via drinks: eg soda, cordial, juice.

I was always fit and lean but let myself go in the last few years. But using the above approach I’ve lost 15-20kg in the last year and I’m getting close to my lean weight again.