Go to Settings>Storage. First look at the Available Space and the Cached Data. It will take a few Seconds before the data is presented. The Available data should be greater than 100 MB or 0.1 GB. If the Cached Data is greater than 50 MB it can be cleared by touching it and then OK to clear Cached Data. It will not clear any data used by the apps and OS. It will increase again as the tablet is used. Next touch Used Space. That will show where the Space is being used. Application data usage can be reduced by moving a portion of each app which has the option to the external SD card or SD card, whichever it is called, if you have 4.2.2 or later. The earlier Jelly Bean and ICS did not have that option. You have to go to Application Manager and go app by app to check and move a portion of the app to the SD cart if the "Move to SD card " is available. It may not be displayed, may be dimed out or may already be moved and display "Move to device storage".
The last option is to uninstall the largest apps which you are willing to give up and remove or move to the external SD card some of the music and videos if they use a large amount of storage.
The final the "if everything fails" action is to do a "Factory data reset" under Backup and reset. This removes ALL your installed apps, data, pictures, videos, files etc. This restores the tablet to the condition it was in when you took it out of the box on day 1. Obviously this step requires backup of any data/apps you can't reinstall for free or don't have backups of somewhere.
