Nodes Contain Array Data Sets In A Linked List?

TL,DR: observe the nodes just below, that is the data each node in the link list contains. How do I iterate through the entire list to reach the last element (H), so I can add an element right after it?

So I have 4 nodes doubly linked with two dummy nodes for head and tail:

head
node1 = {A}
node2 = {null, B}
node3 = {C, null, D, E}
node4 = {null, F, null, G, null, null, H, null}
tail

Ok, so since the list only contains 8 elements that are not null, its size is actually 8 correct? So now lets say I have an add method that has

add(E item) and inserts the item at the end of the list. So I can get to the last node with tail.previous(), but then how do I iterate to the end so I can add the item after the last item in the list (H). I guess I don't know how you only access one nodes data when that data is an array with empty spaces.

Here is the entire Node code:

Also, I can't just iterate through the whole thing because I am not supposed to. I am supposed to just find the right node and iterate through that only.how to maneuver around a linked list containing nodes where each node contains an array.

/**
* Node class that makes up a DoublingList. Feel free to add methods /
* constructors / variables you might find useful in here.
*/
public class Node<E> {
 
/**
* The node that comes after this one in the list

[code]....