How To Insert Item Into Array

I don't really get the concept of how I "insert" an item into an array. I get a cannot find symbol error when I try to. I think its because I'm losing focus. What sort of code would "insert" an item into an array? I just want a goal of conceptually how I would do it.

Anyways, here are the instructions for the exercise:

Write a new class method, insert, for the Item class that takes three arguments - an Item[] array, an Item newItem, and an int k - and inserts newItem into array at index k, discarding the last item of the array (that is, the item originally at index array.length - 1).

Here is the uneditable code:
 
public class Item {
private int myN;
  public Item( int n ) {
myN = n;
} 
public String toString()

[Code] ....

I get a cannot find symbol error, but I thought I was doing as I was supposed to. I thought you had to have an ArrayList to be able to insert or delete an item from an array. How can you take a primitive object, like an array, and insert something into it. My idea of it was a[i] would be replaced with a[i + 1]. I know I'm getting this concept wrong because that's what I tried to do.