This app was mentioned in 3 comments, with an average of 2.67 upvotes
The single best piece of advice I think I can give you is to start doing practice NCLEX questions/tests NOW.
Every RN program is going to be different in some ways, but they ALL are striving for you to pass the NCLEX 1st try (only try that matters for their stats)
Therefore, practice NCLEX questions will help in every case.
Saunders makes an excellent NCLEX prep book. In addition, I use this app. Yes it is worth $30. Finally, the "X Made Incredibly Easy" series of books is very good for understanding your course materials, especially if your textbook is written at a more advanced level (Brunner!)
Best of luck to you! It will be the hardest thing you've ever done (being a CNA has prepared you for nursing work, not nursing education) but it will be so, so worth it when you make it through.
Here is their nclex mastery they have free 24 hour trials so you should definitely give it a try and if you are really struggling they can even give help via email phone or online chat to help you https://play.google.com/store/apps/details?id=hlt.nursing.com
Is this the NCLEX Mastery app you used?
https://play.google.com/store/apps/details?id=hlt.nursing.com