I am a 18 year old guy and my waist is 28 and butt size is 32 what exerises can i do indoor to increase my waist size?

Protein diet: without knowing your other body measurements and BM etc, you may be a naturally thin built person. If that is the case, you need protein rich diet to build muscle, Try protein shakes before choosing midriff exercises for abdomen and quads, 30 minutes, 4-5 times a week. Remember, you need to build your stamina for exercises and increased protein load for your body.