How do you loose stomach fat?

I do gymnastics and when I’m stood up and stretching it’s fine because my stomach is totally flat, so I can get my head to my knee and stuff.
When I’m sat down I can’t get flat because loads of stomach fat has all built up and it’s all yuckkk!
What excersizes/stretches help tone stomach?
I’d also like to loose a bit of thigh, if you know any excersizes for that. TYVM. ^_^
i’m 5’6 & eight stone :]