Losing weight, in its basic sense, is about taking in fewer calories that you burn during a day. It takes burning 3500 more calories than you eat to lose a pound. So, if you burn 500 fewer calories than you eat each day, you will lose a pound a week (500 X 7 = 3500). Have you set up your profile in FitDay and put in your starting weight and a weight goal? That should give you an idea of how many calories you should eat each day to meet your goal. That's probably the best place to start, in addition to logging all your food on the site so you have an accurate idea of how much you are eating.
It's about taking one thing at a time. A lot of people find it easier to change one thing at a time, such as stopping soda or substituting a piece of fruit for their usual evening snack. As time goes on, you can get more into the ratios of fat, carbs, and protein, but for now, just try to get a baseline on the calories.
And now that you don't have to be perfect, you can be good.