first off,your asking the wrong question first-you should be asking about diet and training first...i know i know...your probably rollin ur eyes about now..but read on...every newb has to ask/learn sometime...and i wish that i had put diet first years ago!
Ahem!!!!!
I agree with a lot that juggernaut7 & Complete Muscle have posted. But I suggest eating a "clean" diet but upping the cals so you aren't burning the cals off!
Take your current body weigth x 15 = maintance cal intake
Take your body weight x 17 (or 18) = growth cals! (you are intaking more than your body burns...means you will grow..but you'll gain a belly as well...fair trade off!)
Clean diet is (IMO): Lean meat (sirloin, chicken breast, fish), good complex carb (sweet or baked potato, rice, oatmeal) and a fiber carb (greens...turip, collard, spinch, broccoli).
You can have a cheat meal once or twice a week (pizza, burger,..)
I also suggest a higher protein diet: 40% protein, 30% carbs (complex and fiber), 30% fat (extra vir olive oil, flax seed, EFA)
This will help you build lean muscle with the least amount of added body fat. But this is a strict diet...I should say a strict eating life style!