I know exactly how you feel at this point in time, because before I began bodybuilding (a few years ago now), I was completely clueless just like you. It can be so amazingly overwhelming not knowing how to achieve big results for your own body - especially considering that every man and his dog has a different approach to success.
I'll begin by saying that in order to make a significant improvement in your physique, this requires education, consistency and dedication. You need to know the fundamentals to your nutrition and exercise routine. You then need to apply this theory into a consistent training and eating regime. From there you must remain dedicated and focussed - it is all too easy to undo your hard work by slacking off.
Because everyone is just so different, and I don't know your specific goals, it is very difficult for me (or anyone for that matter) to advise you to do A-B-C. For example, to become fitter, what would this entail - becoming stronger or building muscle or being able to sprint faster or being able to run for longer distances? Depending upon your specific goals, your training would vary significantly.
Your nutrition will also follow a similar path. If you wanted to build muscle, you would need to consume more than if you wanted to lose fat, for example. I can say however, for general health, the more natural your diet is, the better you will feel within yourself. Disregarding supplementation, if you attempt to eliminate as much processed food from your diet, you will generally achieve health and fitness goals faster. For example - dumping the processed breads, cakes, packaged foods etc. for natural vegetables, fruits, grains, meats, dairy and eggs.
Whilst I realise that this is a very vague answer, as a fitness professional, it is near impossible for me to provide you with an effective plan as mentioned above. I can however suggest that you begin with a course that I am publishing to assist with your education. This will help you to understand the basics of both exercise and diet - and how to implement these into your lifestyle in order to achieve your goals:
I hope this helps. If you would like some specific plans drawn up with support, I do offer both face-to-face and online personal training services. Click here for more information.
All the best.