I need to get back into shape! Help!

I recently checked my weight and I gained 20 pounds! I'm not surprised because I have noticed that I have been gaining weight... I really need to get back my shape but I don't know where to start. I want that hourglass figure. So a butt with a slim waist and flat stomach. And a high Metabolism. Does anyone know any apps or websites that are free that can work with me? I can't do it alone so I need a personal trainer type of thing. So does anyone know any apps that can guide me to my goal?