Unless you want to develop nice breasts, your bollocks to shrink and develop uncontrollable mood swings, steroids are best avoided.
Two months is not an awfully long time to build significant mass, but you can certainly make a difference in that time. Concentrate on compound exercises such as bench presses, military presses, cleans etc, which work more than one muscle group and have an overall anabolic effect. To get defined abs, you need to strip away any overlying fat by increasing cardio. However, it is very difficult to simultaneously loose fat and gain muscle: you're body is trying to do two opposite processes at the same time. Most people put on a little fat when they're in a bulking phase, so it depends on whether mass or definition is your short-term goal.