There have been lots of posts and solutions posted on this recently. Just do a search on the forum.
Solutions include deleting cache (using xunity maintenance), deleting unused apps, some apps can be copied to sd card (but not all, go to android - settings - apps and see if the move to sd card option is highlighted). Open Es file explorer tools and run the sd card analyser to see where storage is being used. Often it is temp files in kodi which can be deleted. Move any photos and music to off line storage. Check any old zip files and apk files in download folder and delete. At least 1 person asks everyday so you shouldn't have trouble finding solutions. Some of the support guys have posted help videos as well.