I want to join a gym, 17f

Hii I’m 17f and I weigh around 54kgs and I am 155cm and I want to join the gym to build my physique and get better self image 😭😭🙏, my parents think it’s going to ruin my body and stuff but they agreed after I kept on pleading them with it, also I have been gaining weight sitting around and I keep on procrastinating home workouts that’s why I decided to join the gym but I am way too scared what if they judge me there in the gym and all 😭😭😭 any advice