How can I get a bigger but??
squats. Do not gain weight and do not listen to that other persons advice. Doing squats and leg lifts with weight (resistance) will tone your muscles and bulk up your tooshy. Thats why people who ride bikes have big booties, they train their rectus femoris, gluteous medius and maximus to eat the fat and bulk the muscle.
the only way to do that is to gain a lot of weight all over your body making you fat/overweight or by getting bum implants when your 18