Part of Noom includes a food journal, where you track your meals for the day. Noom gives you a daily calorie target (which you can adjust in the settings, and might be higher or lower depending on how much activity you've done that day). This feature also categorizes the food you log as green, yellow, or red, and how much of each category you should aim for.
To stick to your daily calorie target, it's helpful to plan your meals out in advance. You don't need to do a full meal prep for the week (although that might be helpful), but I find logging my day's worth of meals and snacks in the morning helps me stay on track and mindful of where I'm at in my calorie budget. Of course, I don't always stick to the day's plan 100 percent and will adjust accordingly, but having a calorie estimate in mind ahead of time helps me stay on track.