Steroids are not magic beans. You don't take them in isolation and expect results.
Here is the best explanation for the necessity of intense physical exercise for muscle growth.
"We all understand that weight training is fundamental to growing muscle tissue.
To date, no "sit on your ass and get huge and ripped" pill has been invented. The reason is that a number of changes take place in your local muscle tissues during intense training that are vital to the growth process. Without these early changes, growth is difficult if not impossible to stimulate. So for our purposes, we will start here. Training is the "trigger" in the anabolic process. More specifically, it is the localized cellular damage that weight training produces that will first set us down the road of anabolism. The body will respond by repairing this damage, and in the process will try to adapt by making itself stronger. Muscle growth is always a circular process, with a step back (damage) being necessary to take any steps forward."