The above post is spot on for bulking up, remember to eat throughout the day (every 1 and a half hours) if possible as the body will absorb protien and carbs better instead of large meals.
As for steroids i wouldnt go down that route as its just a quick fix...you will lose much of what you put on when you come off it as your body will retain much water, in any case you can if you train and eat properly get as big as someone who is on the juice, the side effects of steroids can be devastating to the organs years down the line...take a look at the pic i posted in the thread 'what do you weigh and what do you bench' to see what can be achieved naturally.