Mate it sounds as if you have basically never trained with any seriousness, I think you should just focus on the basics:
CLEAN YOUR DIET UP: this does not mean eating less, most times it means eating more, but of wholesome healthy foods. What foods you may ask? You can research that, I call it eating like an adult, you know most of the time if food is good or bad......just be sure to consume more protein than you have been.
START A GOOD PROGRAM: No, I'm not going to tell you which one, do your research, KingBeef is a name to look for when finding a bloody good program on T-Nation. THAN STICK TO IT FOR 3 MONTHS! (at least)
BE CONSISTANT: Don't miss a workout, stick to the program you chose, don't change it every couple of weeks because of the latest and greatest bull shit coming out of a magazine.
Your body composition will naturally change with this simple basic information, once you have a few months under your belt of consistant training than you will be able to decide what you want to do, either try cutting up a bit, or keep going and building some decent mass. Either way, you will have a better understanding of yourself and will be more able to decide what to do next. Remember, ask questions if you get stuck with your training and most times you will get helped out, just don't expect everyone to be your personal guides in your training journey. If you want critique of an exercise movement, post a vid, anything else is next to usless for us to give any advice on.
More than anything, welcome to the iron game mate, I hope you stick to it and get what you want from it.
Good luck with it mate.