Unfortunately you don't define what you mean with muscular. You get different types of muscular, what I call your rock climbing type and your gym type. Do you want to look muscular or actually be physically strong. There is a difference. You only build about 25 pounds maximum muscle a year depending on your diet and the type of exercise you do. Furthermore Also what most people (and this is only my opinion - I'm not a professional trainer do) is eat way too much protein and then gain fat rather than muscle. Best thing is to do a variety of exercise and don't only spend time in the gym. Train your muscle till they are tired, don't overtrain and don't do too much to fast. Also giving your body time to recoup is very important to build muscle and gain strenght.
And as a note, for every .5 pounds of muscle you need to put on at least a pound of weight, so you'll have to eat quite a bit more for muscle.
Check out my How To, it may help - http://www.funadvice.com/howto/pack