Try to pick up a physical activity you enjoy. Such as walking, running or swimming. Aim for roughly 30 - 60 minutes of physical activity every day. You cant spot drop. weight comes off where it wants to but if youre looking for a flat stomach you can try some ab exercises. Theres a youtube channel called diet health where they give new exercises every week. Give it a shot. Also make sure to eat three meals and three snacks a day. Also drink plenty of water. not only does it help you lose weight and prevent bloating but it makes you feel more energized. best of luck
For your height, you are not overweight. Assuming that your mom provides balanced meals, you can try controlling your portions sizes a bit, but since you aren't overweight, even that should not be necessary.
Since you are mostly looking for a flat stomach, I'd suggest that maybe you only need to tone your muscles, which can be done with a simple exercise routine, or even a brisk 30 minute walk each day. You can watch a lot of videos online that will help you firm up your muscles.
Good luck.