Thanks for your inquiry.
If you sign-in to your Theme Forest account and re-download circle flip, then replace all the theme’s files, this would not affect your posts or pages, just keep a backup of your theme options just in case. ( reference http://docs.creiden.com/circleflip/theme-options-2/backup-restore/ )
Thanks to your feedback we’ll make sure we add a detailed guide to updating Circle Flip.
Let us know if you need assistance updating, we would be glad to help, and feel free to rate Circle Flip on Theme Forest if you like it 🙂