Program is C I don't understand the array portion at least how to be able to add elements to an array

Create a menu-driven program that will accept a list of non-negative integers from the keyboard, calculate the mean and median values and display those values on the screen. Your menu should have 4 options: Add a number to the array (list) Display the mean Display the median 1. 2. 3. 4 Quit Program particulars: Use an integer array to store the integers entered by the user. There must be error checking on the input integer. If it is negative, the program will print an error message and re-prompt. This process will continue until a non-negative integer is entered. There must be error checking on the menu choice entered. If the user enters a choice not on the menu, the program will print an error message, re-display the menu and re-prompt. This process will continue until valid input is entered. Your solution must be modular. The design of your functions is up to you, but the rules of highly cohesive" and "loosely coupled must be followed