Getting my Body Right?

Ok so I'm  like 17 and a senior. I mean i have a nice body I've always had an hourglass shape.
However for actually being in shape? lol I be so it if breath walking up stairs I never go on diets because I like to eat lol I'm about 5'8 140 pounds curvy just when I go to college I plan on being in the band (colorguard 🎌) and I know I'm going to need to get my body in shape and stuff for that but also In general I was to be healthier, like eating healthier and working out ( I kinda want abs lol) but any suggestions and where to start?