How can I do this step by step?

Design a Pseudo-code and a flowchart that asks for the number of fat and calories in a food item. Validate the input as follows: Make sure the number of fat grams and calories is not less then 0. According to the nutritional formulas, the number of calories cannot exceed fat grams * 9. Make sure that the number of calories entered is not greater than fat grams * 9. Once correct data has been entered, the program should calculate and display the percentage of calories that come from fat. using the formula: percentage of calories from fat= (Fat grams * 9) / Calories. If the results of the formula are less than 0.3, the program should display a message indicating the food is low in fat.