Definitely add protein to your diet IF you are not getting enough. Rule of thumb is 1 gram of protein for every pound of bodyweight. Just remember to drink lots of water (work your way up to 1 gallon a day) and to actually work out (I know some people who think just drinking protein shakes will make them big).
I'm assuming you know the basics of working out, but take it from someone who screwed up and is now doing things right. Form is 100 times more important the the weight you are lifting. Dont swing weight and dont use momentum, always control your weight when going "down" (negative) or "up" (positive).
stay focused and visualize your muscles growing as you work out and you will be get big and feel great in no time.
good luck, and check out : the
forums here for tips on diet and stuff.
also check out :
workout animations for good form and exercise descriptions.