I agree about the books, though I would suggest using the confuser onl to test yourself once you have read the Thom book.
In the exam you will need to plan a route on a chart, use the flight computer to work out the full details such as headings, groundspeeds, time and fuel. You will then have to answer questions about the route and probably an airfield (with extract from the AIP to interpret), and show knowledge of radio navigation aids.
It is very difficult to tell you how to do any of these things except face-to-face, so work through Thom and ask your instructor to explain or demonstrate anything you have problems with. The flight computer causes confusion, but is fairly straight-forward if soemone shows you. Practice all the techniques, there are questions in Thom but this is where the confuser comes in very handy.
Best of luck!
Send Clowns
Navigation Instructor
BCFT