Train a couple more years naturally, before you turn to steroids for a few reasons 1) you are too young 2) you need to build a solid base 3) You need to get your diet pretty close to perfect before you start a cycle

Check out the diet forum (especially the "stickies") about diets to gain weight, lose weight etc...

For now I would get some good creatine, glutamine, whey protein, and a multi-vitamin. Check out the supplements forum for good info about that.

And for the next couple years research, research, research, because these can be dangerous drugs if not taken properly.