Here is the answer to this question.
In order to lose weight, you have to subtract calories. Safe weight loss is 1-2 lbs/week, so in order to lose 1 lb/week, you'd have to drop 500 calories from your BMR each day (1 lb is equal to 3500 calories, so 500 calories X 7 days = 3500 calories or 1 lb). OR you can drop 250 calories from your diet and increase exercise to use an additional 250 calories.
Changing up calorie counts and exercises will help prevent plateau.
You enter your weight, gender, age, height etc . And the app tells you how many daily calories you should personally consume to lose weight. You have to enter what you ate and its calories and it then also tells you how many more calories you gave to consume that day.