Can anyone please explain how can I implement my code to add an element to the back of a circular arraydeque?

Question

I have declared a class ArrayDeque which takes in an Circular Array A1 and I want to try and add an element to the back of the Array.

I have only declared variable such as head and tail and size and intialized them. However, I'm completely stuck on what am I supposed to do next.

Here is my code so far:

public class ArrayDeque<T> {
    private int volume = 0;
    private int size = 0;
    private int head = 0;
    private int tail = 0;
    private Object[] A1;

    public ArrayDeque(int volume) {
        this.volume = volume;
        A1 = new Object[volume];
    }

    public void addLast(T data) {

        }

My addLast(T data) is completely empty because I genuinely have no idea where to start or whatsoever.

Can anyone please explain what I have to here.

Please also provide explanations since I'm trying my best to figure out how this works.