Hi,
If you are talking about the ''CBS All Access'' app then I think that you will ''not be able to use it'' on your tablet.
According to the information in this link, the ''minimum system requirements'' for the app to work is Android Ver. 5.0 and higher. (Scroll down the page to see the Additional Information section).
https://play.google.com/store/apps/details?id=com.cbs.ott&hl=en
According to this link your tablet is running Android Ver. 4.01 (Jelly Bean). I have checked the Nextbook website and there are no firmware updates available from Nextbook for your model tablet.
http://nextbooktabletguide.com/nextbook-nx008hd8g-specifications/