Read (or listen to) the book a few times. If you don't learn well that way, write your own flash cards or notes (based on the book) to help you learn better.
(Someone on here recommended a CBC documentary as an extra way of becoming familiar with the material, so if that works for you then that may be worthwhile, too. But remember that only what's in the book is part of the test, so seeking out other information sources can only be a studying aid. The book should be your focus.)
Use the practice sites to check that you remember things and to get used to the format of the test, but not to learn the material. The actual test questions are likely to be different from the ones on any of the practice sites, so using the practice sites to learn the material is not a good approach.