its a must to have a shotgun fitted. proper fit will put you on target quicker than months of practice. most gun store shotguns are designed to fit all until gun manufactures started producing shotguns where you can adjust the stock. proper shotgun fit is basically as follows: look into mirror with shotgun mounted as if you are going to shoot. at maximum you should only see the colored part of your eye. remember always bring the gun to the head not the head to the gun.
for gun club locations look at nssa.com for a range in your area
someone there should help you.
"Don't piss down my back and tell me its rain", Fletcher, Outlaw Josey Wales
Living somewhere between this world and the other, Legends of the Fall