Getting fitter is less complicated than you might think. Diet gurus and fitness coaches may have their uses but the basics are pretty simple.
Look at the INPUTS - what you put into your body in terms of food and drink and so on - and look at the OUTPUTS - what you do with your body in terms of activity and exercise. Fine tuning and small changes in both can make a big difference. All the links you need are here.
(If you're very unfit or haven't exercised for a while, check with a health professional before starting anything more than easy walking.)