This is how I studied:
1. I listened to the Discover CANADA audio book (3 times) on
1.5x speed and at the same time i had the book in hand with a yellow marker. I highlited key notes (dates, names, etc..)
(Audio book link)
2. I practiced online tests on these websites
https://www.apnatoronto.com/canadian-citizenship-test-practice/ (questions in here are quite close to the actual test)
http://www.thecanadiantest.com/citizenship-test
The exam is easy, you have like 10-12 trivial questions and the others are straightforward only if you have read the book a couple of times
All the best to you