Imagine the process as a 3 sided pyramid. You need all three sides to be strong, or it will collapse.
1st side is exercise, 2nd is protein intake, 3rd is sleep.
You obviously need to exercise, but how you do it is important. Resistance training with free weights, hitting 2 related muscle groups per day is the way to go as you start out. I do biceps and back one day, rest, triceps and chest, rest, shoulders and legs (you use your shoulders more than you'd think for leg exercises), rest and repeat. You need to be working each muscle group AT LEAST once per week. You need to be doing at least 3-4 exercises on each muscle group per session, for 3-4 sets of 8-10 reps, reaching exhaustion by your 10th rep or so. That's just a starting point, you can build up from there.
Then there's protein intake, which is the material your body uses to build muscle. Optimum intake is 2.2 grams of protein for every kg of lean muscle in you body. That can be hard to work out, so just push for as close to 2g of protein per day for every kg you weigh.
Your body needs sleep to repair itself, so getting your 8 hours is extremely important in building muscle. Deep REM sleep is when your body is doing most of its maintenance, which is where your bulk will be built.
That's the general idea, everyone wants there to be some magic alternative to hard work and discipline, but there just isn't. Steroids help a lot, but you still need to be out there doing your exercise to exhaustion, eating your protein and getting your sleep.
And I'll also be doing core exercises and cardio on my rest days. From stating out they say it takes up to three months to see any difference in muscle mass as you have to adapt your central nervous system to your new routine, but it will come with time.
