Okay i am 14, and I want to get in shape! please help me!! :)

Some things you might want to know about me: I’m 14, I am pretty skinny (100 lbs) I am out of shape, (running tires me out, i cant do many pushups, etc.) I want to get a six pack, and I am NOT trying to lose weight! I am perfectly confident with my weight. Please give me some tips to get back in shape, and tell me how to get a six pack besides just doing crunches. (not totally ripped just like you can see it when I flex) So give me your best thoughts! Thank you!