I want to add an item when entering the server, how can I do this?

Question

Java

Hi all! I want to add an element when entering the server
Namely, the head, and I don't know how to enter it in the code (I'm a beginner) I will be happy to help :)

package ru.flaks.heartguild;

import org.bukkit.event.Listener;

public class Items implements Listener{

    public void OnJoin() {

    }
}