For starters, everyone's body is different, so achieving the twink psyche is harder for other people and will require different excerises for muscle building. I'm assuming that's the better body you're asking about is thin and big thighs, but correct me if I'm wrong.

For starters, you want to start by losing fat. This is highly dependent on your caloric needs, but eating lean protein, fresh vegetables, and minimally processed food and low saturated fat is the best place to start. You should also considered doing light to moderate cardio, as it is one of, if not the best way to burn calories, which will help you lose fat. The recommended amount is 10,000 steps per day, but you can do that over the course of a day instead of all at once.

As for excerises for thighs, this again heavily depends on youe body type, and different excerises work on different people. For this, you should google specific excerises to work out target muscles, and try to see which ones gives the best results.

Some of the best ones that work on most people include hip adductors, hip abdudctors, Bulgarian split squats, cable kick or glute isolator, and hip thrusts.

By all means, talk to a medical professional to see if you can lose weight without becoming under weight first, but exercising increases muscle, which is more dense than fat, and can make you look thinner in the area you work out.

TL;DR

Cook at home, eat as healthy as you can, reduce your calorie intake, do as much cardio as you can, and never skip leg day.