I understand the concept of Doubly Linked Lists and I'm trying to understand how you convert them for our upcoming test. Though I know you use prev / precede in your code I'm not exactly sure how to do so.

If you haven't already, get out a piece of paper and some crayons and start drawing little boxes with arrows pointing to each other.

Here is a similar posting of mine from not long ago, replete with pictures.
http://www.cplusplus.com/forum/beginner/19729/#msg102801

Now, using your pencils, draw yourself the following:

1. What would be different between a singly-and doubly linked list?
2. How would you insert a link in a doubly-linked list?

Now you can answer, how does that differ from inserting a link in a singly-linked list?

If you can get that far, you'll ace your test. Good luck!