How do I gain weight???

Angie

I’m 13, 5’3 and I only weigh 90lbs. I really wanna gain weight I just can’t. I don’t have an appetite. You can sometimes see my ribs. I wanna have some curve to my body and I want a butt. Anything that I should try?? This is my body rn and it doesn’t look bad but it kinda is and I’m worried ⬇️⬇️