Your best bet when studying anything is using multiple sources. When I was studying for my Network+, I didn't understand DNS in the first study guide. Another book had a different approach to explaining that really helped me understand it better. Now if only I could do the same for subnetting, I'd be golden!
When you're using the internet, you have tons of sources. You could even look up the exam objectives, and google search each one and check out different material from other sites, as well as Wikipedia, forum posts, etc.
As for your specific question, I've never even heard of Train Signal. Is it a book, or something else?
Try checking out this study guide.
http://www.proprofs.com/certification/c ... ndex.shtml